1 00:00:26,640 --> 00:00:28,600 DAVID ATTENBOROUGH: A Perfect Planet. 2 00:00:36,080 --> 00:00:41,720 All life in the oceans depends on the continuous movement of water. 3 00:00:55,040 --> 00:00:57,360 There are not five separate oceans on Earth... 4 00:00:58,880 --> 00:01:00,400 ..but just one... 5 00:01:00,400 --> 00:01:04,800 ..whose parts are linked by powerful, unceasing currents. 6 00:01:07,000 --> 00:01:11,200 Every drop of seawater on Earth rides these currents, 7 00:01:11,200 --> 00:01:15,520 taking a thousand years to complete a single circuit. 8 00:01:19,040 --> 00:01:21,680 And where there are currents... 9 00:01:21,680 --> 00:01:23,440 ..there is life. 10 00:01:40,440 --> 00:01:42,720 Off the coast of South Africa, 11 00:01:42,720 --> 00:01:44,440 dolphins are on the hunt. 12 00:01:55,280 --> 00:01:58,280 They have found a cold-water current 13 00:01:58,280 --> 00:02:01,440 and are now travelling along it looking for food. 14 00:02:04,760 --> 00:02:07,080 Gannets follow them. 15 00:02:08,840 --> 00:02:12,680 They know that doing so is the fastest way to a meal. 16 00:02:18,480 --> 00:02:20,160 A shoal of mackerel... 17 00:02:20,160 --> 00:02:22,520 ..just what the dolphins have been looking for. 18 00:02:29,320 --> 00:02:33,160 They encircle the fish, driving them into a bait ball, 19 00:02:33,160 --> 00:02:35,480 and then trap them against the surface 20 00:02:35,480 --> 00:02:37,840 to prevent them from escaping to deeper water. 21 00:02:43,360 --> 00:02:47,280 Now, the fish are within range of the dive-bombing gannets, 22 00:02:47,280 --> 00:02:49,560 who hit the water at 50mph. 23 00:03:13,440 --> 00:03:17,480 A sudden gathering of thousands of predators brought together 24 00:03:17,480 --> 00:03:20,480 by the flow of currents. 25 00:03:35,960 --> 00:03:38,840 Last to the feast are sharks. 26 00:04:01,720 --> 00:04:04,240 In these vast, open waters, 27 00:04:04,240 --> 00:04:08,640 finding food would be all but impossible without currents... 28 00:04:09,600 --> 00:04:13,320 ..the highways of the seas that bring this life together. 29 00:04:18,200 --> 00:04:21,280 When the bait ball has been dispersed, 30 00:04:21,280 --> 00:04:25,080 all that is left are scales drifting downwards. 31 00:04:30,080 --> 00:04:34,120 They are part of a slow, never-ending blizzard 32 00:04:34,120 --> 00:04:39,320 of organic waste that eventually settles on the sea floor. 33 00:04:42,320 --> 00:04:45,560 But it doesn't stay here forever. 34 00:04:45,560 --> 00:04:49,120 The currents sweep it back up into the sunlit surface waters... 35 00:04:50,440 --> 00:04:53,960 ..where it nourishes clouds of phytoplankton... 36 00:04:56,240 --> 00:05:01,120 ..simple microscopic plants that are the pastures of the seas. 37 00:05:10,840 --> 00:05:13,680 There are thousands of different kinds, 38 00:05:13,680 --> 00:05:19,200 and together they produce half of all the oxygen in the atmosphere... 39 00:05:19,200 --> 00:05:23,360 ..more than all our forests and jungles combined. 40 00:05:25,520 --> 00:05:27,960 And, by absorbing carbon, 41 00:05:27,960 --> 00:05:32,000 they are our greatest ally in combating climate change. 42 00:05:37,400 --> 00:05:42,800 Plankton are the foundation of almost all life in the ocean, 43 00:05:42,800 --> 00:05:45,760 for, in those places where the currents bring nutrients 44 00:05:45,760 --> 00:05:49,600 to the surface, they multiply in astonishing numbers... 45 00:05:51,280 --> 00:05:53,560 ..turning the ocean green. 46 00:05:59,720 --> 00:06:04,560 The currents travelling through our oceans bring life to seas 47 00:06:04,560 --> 00:06:07,720 that would otherwise be marine deserts. 48 00:06:12,120 --> 00:06:16,360 The Galapagos Islands lie in the path of one of them, 49 00:06:16,360 --> 00:06:18,640 the deep-flowing Cromwell Current 50 00:06:18,640 --> 00:06:21,640 that runs for 6,000 miles across the Pacific. 51 00:06:25,760 --> 00:06:28,360 As it approaches Fernandina Island, 52 00:06:28,360 --> 00:06:31,720 it rises and delivers nutrients into its shallows. 53 00:06:44,960 --> 00:06:50,200 And it also brings life to this otherwise barren island. 54 00:07:07,640 --> 00:07:09,560 Iguanas. 55 00:07:11,160 --> 00:07:13,200 There are thousands of them. 56 00:07:20,760 --> 00:07:25,040 And yet there's nothing on the island for these vegetarians to eat. 57 00:07:27,720 --> 00:07:30,120 Or... 58 00:07:30,120 --> 00:07:31,440 ..almost nothing. 59 00:07:33,760 --> 00:07:38,440 Cormorants bring seaweed ashore with which to make their nests. 60 00:07:40,000 --> 00:07:43,000 But what is building material for a cormorant 61 00:07:43,000 --> 00:07:45,520 is food for an iguana. 62 00:07:51,480 --> 00:07:54,280 Both these species evolved here, 63 00:07:54,280 --> 00:07:57,200 but that doesn't necessarily make them good neighbours. 64 00:08:02,200 --> 00:08:03,520 No matter. 65 00:08:03,520 --> 00:08:06,200 He knows where there's more elsewhere. 66 00:08:08,320 --> 00:08:09,920 He's a marine iguana... 67 00:08:15,160 --> 00:08:17,480 ..the only lizard in the world 68 00:08:17,480 --> 00:08:19,320 that gets its food from the sea. 69 00:08:32,120 --> 00:08:34,920 The seaweed on which he totally relies 70 00:08:34,920 --> 00:08:37,200 only grows in abundance here 71 00:08:37,200 --> 00:08:40,880 because of the nutrients brought by the Cromwell Current. 72 00:08:47,600 --> 00:08:51,640 Once in the water, he has just 30 minutes to find food. 73 00:09:00,000 --> 00:09:01,800 Any longer than that, 74 00:09:01,800 --> 00:09:04,760 and his muscles will seize up and he'll drown... 75 00:09:06,200 --> 00:09:10,200 ..for, like most reptiles, he can't handle the cold. 76 00:09:19,120 --> 00:09:23,000 Chilly water isn't a problem for a warm-blooded cormorant. 77 00:09:24,720 --> 00:09:27,080 She can swim in it all day, 78 00:09:27,080 --> 00:09:29,600 but can only hold her breath for a few minutes. 79 00:09:36,920 --> 00:09:38,960 He, on the other hand, 80 00:09:38,960 --> 00:09:41,520 completes his whole half-hour trip 81 00:09:41,520 --> 00:09:43,680 on one single breath. 82 00:09:45,600 --> 00:09:48,040 His flat face and sharp teeth 83 00:09:48,040 --> 00:09:51,280 make him an efficient seaweed-cropping machine, 84 00:09:51,280 --> 00:09:54,040 but with the clock ticking, he must eat fast. 85 00:09:58,440 --> 00:10:00,960 The cormorant, having caught its fish... 86 00:10:01,960 --> 00:10:03,480 ..goes back to the surface. 87 00:10:06,080 --> 00:10:08,000 One last mouthful, 88 00:10:08,000 --> 00:10:11,160 and it's also time for the iguana to head for home. 89 00:10:14,560 --> 00:10:18,240 But to stop his muscles from seizing up in the cold water, 90 00:10:18,240 --> 00:10:19,920 he must get back quickly. 91 00:10:24,360 --> 00:10:26,800 So he could do without the attentions 92 00:10:26,800 --> 00:10:28,800 of an inquisitive sea lion. 93 00:10:52,040 --> 00:10:54,480 Dry land is now just 30 metres away, 94 00:10:55,880 --> 00:10:58,840 but the biggest hurdle is still to come. 95 00:11:08,560 --> 00:11:11,600 The surging water now fights against him. 96 00:11:18,680 --> 00:11:22,560 He's out, but he's stayed in the cold so long 97 00:11:22,560 --> 00:11:24,200 that he's lost his strength. 98 00:12:05,480 --> 00:12:07,280 And he's made it. 99 00:12:10,080 --> 00:12:14,000 Few reptiles on the planet have to work harder for a meal 100 00:12:14,000 --> 00:12:15,440 than he does. 101 00:12:18,160 --> 00:12:21,920 And, tomorrow, he'll have to do it all over again... 102 00:12:24,440 --> 00:12:26,680 ..unless next time... 103 00:12:26,680 --> 00:12:28,480 ..he can outwit his neighbour. 104 00:12:34,480 --> 00:12:37,440 Over 100,000 marine iguanas live on Fernandina... 105 00:12:39,920 --> 00:12:43,680 ..and each owes its existence to the Cromwell Current 106 00:12:43,680 --> 00:12:45,840 that brings nutrients to these shores. 107 00:12:48,400 --> 00:12:52,080 But there is another, much bigger, current 108 00:12:52,080 --> 00:12:56,400 which carries water from the Pacific into the Indian Ocean. 109 00:12:59,520 --> 00:13:04,440 On this great journey, it travels through the islands of Indonesia, 110 00:13:04,440 --> 00:13:07,240 bringing together life from both oceans. 111 00:13:14,680 --> 00:13:18,880 A third of all the world's reef fish live here. 112 00:13:22,680 --> 00:13:25,640 Some call it the Coral Triangle, 113 00:13:25,640 --> 00:13:28,760 the most diverse marine region on Earth. 114 00:13:37,160 --> 00:13:40,960 The variety here is dazzling, not just of coral, 115 00:13:40,960 --> 00:13:42,840 but of animals of all kinds. 116 00:13:53,280 --> 00:13:57,720 Few are stranger than the flamboyant cuttlefish. 117 00:14:01,120 --> 00:14:04,760 This is a male, just five centimetres long. 118 00:14:09,920 --> 00:14:14,360 Swimming against the current isn't easy when you're small, 119 00:14:14,360 --> 00:14:17,120 so, instead, he prefers to walk... 120 00:14:19,000 --> 00:14:21,040 ..very, very slowly. 121 00:14:25,560 --> 00:14:28,280 He's a master of camouflage. 122 00:14:28,280 --> 00:14:31,040 But, right now, he wants to be noticed. 123 00:14:34,240 --> 00:14:36,320 He's looking for a mate. 124 00:14:37,760 --> 00:14:41,040 His potential partner is a giant, by comparison, 125 00:14:41,040 --> 00:14:42,520 four times his size. 126 00:14:47,760 --> 00:14:49,960 When it comes to courtship, 127 00:14:49,960 --> 00:14:52,520 being flamboyant isn't enough. 128 00:14:58,600 --> 00:15:00,920 To win her over, he must dazzle. 129 00:15:08,160 --> 00:15:11,640 His aim is to deposit a packet of sperm 130 00:15:11,640 --> 00:15:13,560 inside her mouth. 131 00:15:16,920 --> 00:15:19,160 Close... 132 00:15:19,160 --> 00:15:20,560 ..but no cigar. 133 00:15:26,320 --> 00:15:28,680 He'll have to turn up the dazzle. 134 00:15:35,680 --> 00:15:37,120 Take two. 135 00:15:41,920 --> 00:15:43,200 Bingo! 136 00:15:53,720 --> 00:15:55,960 His job is done. 137 00:15:55,960 --> 00:15:59,200 Now she must find somewhere to lay their eggs. 138 00:16:02,320 --> 00:16:05,120 An old shell will do nicely 139 00:16:05,120 --> 00:16:08,040 if she can slip past the present occupant. 140 00:16:13,160 --> 00:16:16,800 She fastens her eggs to the underside of the shell, 141 00:16:16,800 --> 00:16:19,000 where they'll be safe from predators. 142 00:16:32,680 --> 00:16:37,200 The current that brings so much life to the Coral Triangle 143 00:16:37,200 --> 00:16:40,920 now washes the eggs with clean, oxygenated water. 144 00:16:47,600 --> 00:16:51,360 After just three weeks, they start to hatch. 145 00:16:56,040 --> 00:16:58,160 Smaller than a human fingernail, 146 00:16:58,160 --> 00:17:01,520 the hatchlings are now carried by the current 147 00:17:01,520 --> 00:17:03,480 to other parts of the reef. 148 00:17:11,600 --> 00:17:13,920 And, in just a few months, 149 00:17:13,920 --> 00:17:18,120 this young male will be ready to find a female of his own. 150 00:17:24,200 --> 00:17:27,120 By a stroke of cosmic good fortune, 151 00:17:27,120 --> 00:17:29,320 the Earth has a satellite... 152 00:17:29,320 --> 00:17:34,080 ..the moon, which orbits our planet every 27 days. 153 00:17:37,560 --> 00:17:42,840 Its gravitational pull drags our oceans across the planet... 154 00:17:45,320 --> 00:17:47,680 ..and so gives us the tides. 155 00:17:52,960 --> 00:17:56,160 Unlike currents that stir the open ocean, 156 00:17:56,160 --> 00:17:59,280 the tides have their greatest impact on the coasts, 157 00:17:59,280 --> 00:18:03,840 flushing them with nutrients from both sea and land. 158 00:18:06,520 --> 00:18:10,040 And nowhere are they more violent and dramatic than here... 159 00:18:12,280 --> 00:18:15,160 ..Norway's Saltstraumen strait. 160 00:18:17,480 --> 00:18:19,120 Every six hours, 161 00:18:19,120 --> 00:18:21,520 nearly half a billion tonnes of water 162 00:18:21,520 --> 00:18:25,720 are forced through a channel just 150 metres wide. 163 00:18:27,800 --> 00:18:31,240 Its very narrowness accelerates the water... 164 00:18:32,680 --> 00:18:37,200 ..making this the strongest tidal pull in the world. 165 00:18:51,920 --> 00:18:54,720 Most animals caught here would be swept away. 166 00:18:58,200 --> 00:19:01,120 But not these tidal specialists. 167 00:19:01,120 --> 00:19:04,080 Eiders are one of the few ducks 168 00:19:04,080 --> 00:19:08,080 that depend totally on the ocean for their survival. 169 00:19:10,720 --> 00:19:13,360 And they're the only kind strong enough 170 00:19:13,360 --> 00:19:16,640 to live permanently in these racing waters. 171 00:19:24,160 --> 00:19:27,400 But there is food here, and in great quantity, 172 00:19:27,400 --> 00:19:29,000 for any that can gather it... 173 00:19:30,640 --> 00:19:32,040 ..mussels. 174 00:19:33,560 --> 00:19:38,880 They filter out particles of food brought to them by the tide. 175 00:19:40,040 --> 00:19:42,360 And eider ducks love mussels. 176 00:19:45,800 --> 00:19:47,880 The challenge is reaching them. 177 00:20:05,480 --> 00:20:07,800 Eiders seem to be the only creatures 178 00:20:07,800 --> 00:20:11,080 that can hold their own in the fast-flowing water... 179 00:20:14,000 --> 00:20:16,320 ..so they have the mussels all to themselves. 180 00:20:19,040 --> 00:20:22,080 They swallow them whole, shell and all. 181 00:20:26,160 --> 00:20:30,000 Each eider duck eats hundreds of mussels a day... 182 00:20:31,200 --> 00:20:34,840 ..a year-round feast that no others can reach. 183 00:20:46,400 --> 00:20:49,320 The tides here owe their power 184 00:20:49,320 --> 00:20:52,200 to the unique geography of the coastline. 185 00:20:53,400 --> 00:20:55,880 But, elsewhere in our oceans, 186 00:20:55,880 --> 00:21:00,360 the lay of the land influences tides in a very different way. 187 00:21:03,360 --> 00:21:05,320 Here in the Bahamas, 188 00:21:05,320 --> 00:21:09,640 wide, shallow sandbanks mean the tide moves gently 189 00:21:09,640 --> 00:21:12,400 over the sea floor... 190 00:21:12,400 --> 00:21:14,960 ..turning what would be a sandy desert 191 00:21:14,960 --> 00:21:17,400 into a rich underwater habitat. 192 00:21:21,000 --> 00:21:25,400 This is the home of garden eels and razorfish. 193 00:21:29,600 --> 00:21:34,360 And fresh food arrives for them from deeper waters twice a day. 194 00:21:37,240 --> 00:21:39,240 Life seems unhurried and gentle... 195 00:21:42,040 --> 00:21:45,000 ..but there is trouble in paradise. 196 00:21:48,080 --> 00:21:51,680 These bottlenose dolphins eat razorfish, 197 00:21:51,680 --> 00:21:54,880 and they're not so easily fooled by vanishing tricks. 198 00:22:00,600 --> 00:22:04,480 They scan the sand with echolocating clicks 199 00:22:04,480 --> 00:22:08,840 to discover exactly where the razorfish are hiding. 200 00:22:24,800 --> 00:22:28,120 But knowing where they are is not the same as catching them. 201 00:22:34,560 --> 00:22:37,080 The more the dolphins dig, 202 00:22:37,080 --> 00:22:39,120 the deeper the razorfish burrow. 203 00:22:42,720 --> 00:22:45,440 But it's clearly not deep enough. 204 00:22:55,000 --> 00:22:57,920 Blowing jets of water into the sand 205 00:22:57,920 --> 00:23:01,840 exposes even the most hard-to-reach razorfish. 206 00:23:05,480 --> 00:23:09,720 Before long, the dolphins have had enough and they move on. 207 00:23:12,040 --> 00:23:14,920 It looks as if they have picked the sand clean... 208 00:23:20,160 --> 00:23:22,120 ..but here, at least, 209 00:23:22,120 --> 00:23:25,160 there really are plenty more fish in the sea. 210 00:23:35,360 --> 00:23:39,200 Closer to the land, the same tides bring nourishment 211 00:23:39,200 --> 00:23:42,680 to one of the most threatened of coastal habitats... 212 00:23:43,680 --> 00:23:45,520 ..mangrove forests. 213 00:23:47,080 --> 00:23:49,240 Part land... 214 00:23:49,240 --> 00:23:50,960 ..part sea. 215 00:23:52,880 --> 00:23:55,720 Mangroves are the only trees 216 00:23:55,720 --> 00:23:58,800 capable of surviving in salt water 217 00:23:58,800 --> 00:24:03,080 and are specially adapted to it coming and going twice every day. 218 00:24:10,480 --> 00:24:13,960 As sea water floods in, fish come with it. 219 00:24:15,400 --> 00:24:17,480 Here in the flooded forests, 220 00:24:17,480 --> 00:24:20,920 they can find both food and shelter. 221 00:24:27,480 --> 00:24:30,880 Stingrays ride on the incoming tide. 222 00:24:38,280 --> 00:24:41,520 Other commuters follow. 223 00:24:41,520 --> 00:24:45,000 Young lemon sharks, still far from full-grown, 224 00:24:45,000 --> 00:24:46,880 are looking for food. 225 00:25:01,960 --> 00:25:04,320 When the tide is at its highest, 226 00:25:04,320 --> 00:25:06,520 even adult lemon sharks 227 00:25:06,520 --> 00:25:08,360 can get into the mangroves. 228 00:25:11,480 --> 00:25:15,440 A three-metre female moves cautiously into the shallows. 229 00:25:18,680 --> 00:25:21,040 She can't stay here for long, 230 00:25:21,040 --> 00:25:23,680 but, then, she hasn't come here to hunt. 231 00:25:30,080 --> 00:25:32,880 She's come to give birth... 232 00:25:34,320 --> 00:25:37,080 ..returning to the very place where she was born. 233 00:25:40,920 --> 00:25:44,360 She has nourished the pups inside her body 234 00:25:44,360 --> 00:25:46,680 with a placenta, as we do. 235 00:25:53,360 --> 00:25:56,920 The mangroves provide an ideal nursery for them, 236 00:25:56,920 --> 00:26:00,200 and placing them here gives them an excellent start, 237 00:26:00,200 --> 00:26:03,320 but that is the end of her parental care. 238 00:26:05,240 --> 00:26:09,360 She has to return to deeper water before the tide goes out. 239 00:26:13,720 --> 00:26:16,400 Her young must now fend for themselves. 240 00:26:20,040 --> 00:26:24,640 The pups instinctively take refuge among the roots of the mangroves. 241 00:26:27,720 --> 00:26:31,240 They're so small, they can swim deep 242 00:26:31,240 --> 00:26:33,160 into this tangled labyrinth. 243 00:26:44,600 --> 00:26:46,720 With the tide fast receding, 244 00:26:46,720 --> 00:26:48,720 even they need to find a place 245 00:26:48,720 --> 00:26:51,040 where they won't be left high and dry. 246 00:26:52,760 --> 00:26:54,560 A place like this... 247 00:26:55,840 --> 00:26:59,720 ..a permanent pool in the heart of the mangrove forest. 248 00:27:06,440 --> 00:27:09,240 Only the smallest sharks can get here, 249 00:27:09,240 --> 00:27:11,560 and only at the highest tides. 250 00:27:18,720 --> 00:27:21,640 The pups will spend the next two years here 251 00:27:21,640 --> 00:27:25,400 perfecting the skills that make them one of the ocean's top hunters. 252 00:27:30,320 --> 00:27:32,640 And it seems... 253 00:27:32,640 --> 00:27:34,560 ..that there's a lot to learn. 254 00:27:41,120 --> 00:27:42,520 Got one! 255 00:27:48,560 --> 00:27:53,240 All life at the coasts has to move to the daily rhythm of the tides, 256 00:27:54,480 --> 00:27:57,640 but tides are not the same throughout the year. 257 00:28:03,480 --> 00:28:09,320 Every month, when our planet, the moon and the sun are all aligned, 258 00:28:09,320 --> 00:28:11,960 the increased gravitational pull 259 00:28:11,960 --> 00:28:15,000 produces particularly high tides. 260 00:28:16,400 --> 00:28:20,040 And this triggers a truly extraordinary event 261 00:28:20,040 --> 00:28:22,680 on one particular reef in the central Pacific. 262 00:28:29,520 --> 00:28:32,400 Thousands of resident surgeonfish 263 00:28:32,400 --> 00:28:35,800 begin to assemble on these high tides. 264 00:28:40,320 --> 00:28:44,600 And they are being followed by one of the largest fish in the sea... 265 00:28:51,280 --> 00:28:53,120 ..manta rays. 266 00:29:02,520 --> 00:29:07,480 The rays spend their year moving between coral islands. 267 00:29:09,840 --> 00:29:14,040 But it's only now, when the tide is at its highest 268 00:29:14,040 --> 00:29:16,960 and the surgeonfish have gathered, that they appear 269 00:29:16,960 --> 00:29:19,000 on this particular reef. 270 00:29:22,640 --> 00:29:24,800 Their timing is so perfect 271 00:29:24,800 --> 00:29:27,680 that they rarely have to wait more than an hour 272 00:29:27,680 --> 00:29:29,480 for the event to begin. 273 00:29:55,920 --> 00:30:00,320 At the precise moment when the tide is at its highest, 274 00:30:00,320 --> 00:30:02,480 the surgeonfish begin to spawn. 275 00:30:05,160 --> 00:30:08,280 They release billions of eggs and sperm into the water. 276 00:30:13,400 --> 00:30:16,080 Breeding in this way gives their fertilised eggs 277 00:30:16,080 --> 00:30:19,320 the best chance of being carried on the tide 278 00:30:19,320 --> 00:30:21,880 away from predators that haunt the reef. 279 00:30:25,600 --> 00:30:27,200 All except one. 280 00:30:30,880 --> 00:30:32,880 The mantas move in. 281 00:30:50,600 --> 00:30:53,080 They gorge on the eggs, 282 00:30:53,080 --> 00:30:56,080 filtering them out using specially adapted gills. 283 00:30:58,440 --> 00:31:01,680 If the mantas had arrived just an hour later, 284 00:31:01,680 --> 00:31:04,240 there would have been nothing here for them to eat. 285 00:31:11,640 --> 00:31:15,360 No-one knows how the mantas are so perfectly in tune 286 00:31:15,360 --> 00:31:17,200 with the rhythm of the tides. 287 00:31:23,240 --> 00:31:27,520 But they appear without fail whenever the surgeonfish spawn. 288 00:31:35,840 --> 00:31:37,640 Most of the eggs, however, 289 00:31:37,640 --> 00:31:40,280 are carried out into the open ocean 290 00:31:40,280 --> 00:31:42,880 before the mantas are able to eat them all. 291 00:31:59,200 --> 00:32:05,040 The rhythms of coastal life are influenced by another ocean force. 292 00:32:08,760 --> 00:32:13,200 Winds blowing over the sea so batter the surface 293 00:32:13,200 --> 00:32:15,960 that it begins to rise and fall. 294 00:32:18,040 --> 00:32:19,880 These swells may travel far 295 00:32:19,880 --> 00:32:22,920 and reach the shores of even the most sheltered bays. 296 00:32:24,560 --> 00:32:26,880 As they approach shallower water, 297 00:32:26,880 --> 00:32:28,640 they turn into waves. 298 00:32:33,080 --> 00:32:35,640 A shoal of hardyheads, 299 00:32:35,640 --> 00:32:39,080 close to the beach of Australia's Lizard Island. 300 00:32:40,960 --> 00:32:45,960 The clearness of these glassy waters shows that they lack nutrients. 301 00:32:47,440 --> 00:32:51,400 But the gentle waves expose food hidden in the sand, 302 00:32:51,400 --> 00:32:53,960 and that's what the hardyheads are looking for. 303 00:33:04,040 --> 00:33:06,040 But...they must beware. 304 00:33:09,880 --> 00:33:12,440 Packs of trevally are on the hunt. 305 00:33:21,080 --> 00:33:23,480 The hardyheads stick together. 306 00:33:24,400 --> 00:33:26,160 There's safety in numbers. 307 00:33:27,640 --> 00:33:29,720 But they're vulnerable, nonetheless. 308 00:33:40,840 --> 00:33:43,880 They're so small, they can swim in the shallowest waters... 309 00:33:52,240 --> 00:33:55,520 ..even in the body of the waves themselves, 310 00:33:55,520 --> 00:33:57,760 out of the reach of their enemies. 311 00:34:02,880 --> 00:34:05,760 But trevally aren't their only concern. 312 00:34:15,200 --> 00:34:17,240 Blacktip reef sharks. 313 00:34:18,760 --> 00:34:22,760 They are bigger and more powerful than trevally... 314 00:34:24,640 --> 00:34:26,880 ..but not as fast or as agile. 315 00:34:31,960 --> 00:34:34,720 The hardyheads are well aware of them, 316 00:34:34,720 --> 00:34:37,360 but, so long as they stay just out of reach, 317 00:34:37,360 --> 00:34:38,880 they have little to fear. 318 00:34:53,240 --> 00:34:56,760 But now the sharks and the trevally join forces. 319 00:35:02,000 --> 00:35:04,760 Together, they enter the shallows, 320 00:35:04,760 --> 00:35:06,920 each looking for a chance to attack. 321 00:35:24,960 --> 00:35:26,840 The trevally make the first move... 322 00:35:28,600 --> 00:35:32,440 ..and the hardyheads take refuge again in the waves. 323 00:35:33,440 --> 00:35:35,920 And this is what the sharks have been waiting for. 324 00:35:40,400 --> 00:35:44,600 Surging forwards, they chase the hardyheads out of the water... 325 00:35:45,640 --> 00:35:49,880 ..beaching themselves in a daring bid to hoover up their prey. 326 00:35:54,360 --> 00:35:56,840 The hardyheads that escape the sharks 327 00:35:56,840 --> 00:35:58,720 swim back out to deeper water... 328 00:36:00,840 --> 00:36:03,200 ..but into the mouths of the trevally. 329 00:36:14,320 --> 00:36:17,760 Now the receding waves help to pull the sharks back 330 00:36:17,760 --> 00:36:19,600 into deeper water. 331 00:36:50,200 --> 00:36:53,760 In the chaos, the sea birds get their chance. 332 00:36:58,720 --> 00:37:01,280 It's a feeding frenzy... 333 00:37:01,280 --> 00:37:03,840 ..in only ten centimetres of water. 334 00:37:16,760 --> 00:37:20,840 The power of waves is dramatically evident 335 00:37:20,840 --> 00:37:22,480 when they crash onto our shores. 336 00:37:25,840 --> 00:37:31,360 But the biggest of all start far away from land, out at sea. 337 00:37:33,760 --> 00:37:37,680 Great storms blowing over the surface of the ocean 338 00:37:37,680 --> 00:37:40,280 raise towering walls of water. 339 00:37:43,800 --> 00:37:47,920 Such giant swells can travel for thousands of miles. 340 00:37:50,480 --> 00:37:52,480 As they approach land, 341 00:37:52,480 --> 00:37:57,200 the shallowing sea floor begins to drag on their undersides, 342 00:37:57,200 --> 00:37:59,320 and they topple forward... 343 00:37:59,320 --> 00:38:00,760 ..and break. 344 00:38:04,560 --> 00:38:08,840 This stirring of the ocean produces great riches. 345 00:38:12,640 --> 00:38:14,720 The Falkland Islands are surrounded 346 00:38:14,720 --> 00:38:16,920 by some of the stormiest waters on Earth... 347 00:38:21,040 --> 00:38:25,600 ..ideal hunting grounds for rockhopper penguins. 348 00:38:27,320 --> 00:38:29,320 It's the breeding season 349 00:38:29,320 --> 00:38:31,000 and, for the last two weeks, 350 00:38:31,000 --> 00:38:33,800 the males have been incubating the eggs by themselves. 351 00:38:36,680 --> 00:38:39,640 They're confined to the nest with nothing to eat, 352 00:38:39,640 --> 00:38:42,280 while the females are out at sea collecting food. 353 00:38:47,000 --> 00:38:51,000 All across the colony, eggs are starting to hatch. 354 00:38:52,960 --> 00:38:56,520 This male now has two youngsters to care for. 355 00:38:59,840 --> 00:39:04,040 But he has no food to give them, and he can't leave them unprotected. 356 00:39:05,760 --> 00:39:08,160 He can do nothing but wait. 357 00:39:18,240 --> 00:39:22,160 The females, after weeks fishing in the stormy seas, 358 00:39:22,160 --> 00:39:25,720 are now heading for home with food in their crops. 359 00:39:29,760 --> 00:39:31,280 There's just one problem. 360 00:39:32,600 --> 00:39:35,640 The colony sits at the top of huge cliffs. 361 00:39:38,680 --> 00:39:42,120 The waves that make feeding so good here 362 00:39:42,120 --> 00:39:45,160 have now become major obstacles. 363 00:39:47,360 --> 00:39:49,440 Timing is vital. 364 00:40:03,640 --> 00:40:05,240 Go too early... 365 00:40:06,240 --> 00:40:08,800 ..and they could be smashed against the rocks. 366 00:40:15,080 --> 00:40:17,880 Too late... 367 00:40:17,880 --> 00:40:20,120 ..and they will be carried back out to sea. 368 00:40:26,360 --> 00:40:28,720 Hooked claws now help to get purchase 369 00:40:28,720 --> 00:40:30,440 on the slippery rocks. 370 00:40:33,920 --> 00:40:35,680 But they're not out of trouble yet. 371 00:40:40,720 --> 00:40:43,800 Success depends on both judgment... 372 00:40:43,800 --> 00:40:45,280 ..and luck. 373 00:41:05,280 --> 00:41:09,240 Time and again, the waves drag her back in. 374 00:41:15,560 --> 00:41:17,520 She has to persevere. 375 00:41:17,520 --> 00:41:22,120 The lives of her chicks depend on her safe return. 376 00:41:54,040 --> 00:41:56,120 Finally... 377 00:41:56,120 --> 00:41:58,200 ..she's made it. 378 00:42:07,520 --> 00:42:10,280 They're not called rockhoppers for nothing. 379 00:42:15,960 --> 00:42:18,200 With one more jump, she's home. 380 00:42:21,680 --> 00:42:23,400 And just in time. 381 00:42:28,560 --> 00:42:30,840 Her chicks are desperately hungry. 382 00:42:38,680 --> 00:42:41,760 This is their first proper meal. 383 00:42:51,640 --> 00:42:55,960 The oceans have sustained life on our planet for millions of years. 384 00:43:00,720 --> 00:43:05,280 But, today, there's growing evidence that this is changing. 385 00:43:11,320 --> 00:43:13,360 As our climate warms, 386 00:43:13,360 --> 00:43:16,880 polar ice sheets are melting at an alarming rate. 387 00:43:20,920 --> 00:43:25,360 In the Arctic alone, 14,000 tonnes of fresh water 388 00:43:25,360 --> 00:43:28,560 are emptying into the sea every second. 389 00:43:36,440 --> 00:43:39,960 This is slowing the flow of currents around the globe. 390 00:43:42,840 --> 00:43:45,920 And, if the atmosphere continues to warm, 391 00:43:45,920 --> 00:43:49,760 ocean circulation could eventually stop altogether. 392 00:43:58,720 --> 00:44:01,880 Our seas would then stagnate, 393 00:44:01,880 --> 00:44:04,640 threatening the life within them. 394 00:44:08,360 --> 00:44:10,960 And there are places in the oceans today 395 00:44:10,960 --> 00:44:13,840 where this is already beginning to happen. 396 00:44:22,640 --> 00:44:24,520 The Gulf of Thailand. 397 00:44:31,680 --> 00:44:34,800 Eden's whales have lived here for generations. 398 00:44:38,320 --> 00:44:40,840 But the world around them is changing. 399 00:44:50,120 --> 00:44:53,800 Today, agricultural pollution flowing from the land... 400 00:44:56,480 --> 00:44:59,320 ..is beginning to suffocate this sea. 401 00:45:09,480 --> 00:45:12,760 Many fish now stay closer to the surface, 402 00:45:12,760 --> 00:45:16,600 where the waters still contain enough oxygen to survive. 403 00:45:21,200 --> 00:45:24,520 Eden's whales depend on these fish. 404 00:45:26,520 --> 00:45:29,120 They swallow huge quantities of water 405 00:45:29,120 --> 00:45:31,200 before filtering out their prey. 406 00:45:36,520 --> 00:45:40,520 It takes a lot of energy to drive their 15-tonne bulk 407 00:45:40,520 --> 00:45:42,400 through the water. 408 00:45:45,200 --> 00:45:47,480 And, with so few fish, 409 00:45:47,480 --> 00:45:50,440 the rewards from feeding like this are barely worth it. 410 00:45:53,040 --> 00:45:55,480 So, to survive here, 411 00:45:55,480 --> 00:45:58,720 the whales have developed a new hunting technique... 412 00:46:03,400 --> 00:46:06,680 ..one that requires almost no effort. 413 00:46:09,760 --> 00:46:12,640 They simply open their mouths... 414 00:46:12,640 --> 00:46:14,040 ..and wait. 415 00:46:19,400 --> 00:46:21,880 The panicked fish jump right in. 416 00:46:29,360 --> 00:46:31,240 Swimming alongside, 417 00:46:31,240 --> 00:46:34,760 another whale scares even more into the open jaws. 418 00:46:46,800 --> 00:46:49,560 With this ingenious new technique, 419 00:46:49,560 --> 00:46:53,400 Eden's whales have found a way to survive the pressures 420 00:46:53,400 --> 00:46:55,760 they now face. 421 00:46:57,240 --> 00:47:01,240 All across the planet, animals are having to adapt 422 00:47:01,240 --> 00:47:03,120 to a changing world. 423 00:47:04,960 --> 00:47:08,600 But the speed of these changes will be too fast for many. 424 00:47:13,960 --> 00:47:19,240 If we could only halt our unrestrained plunder of the ocean, 425 00:47:19,240 --> 00:47:21,920 its habitats and species would recover. 426 00:47:24,800 --> 00:47:27,480 And, at a time when our overexploited lands 427 00:47:27,480 --> 00:47:29,640 are already failing us, 428 00:47:29,640 --> 00:47:32,680 this has never been more important for humanity. 429 00:47:53,560 --> 00:47:57,320 The volcanic island of Fernandina in the Galapagos 430 00:47:57,320 --> 00:48:00,080 is home to two incredible lizards... 431 00:48:02,280 --> 00:48:06,640 ..the land iguana and the marine iguana. 432 00:48:08,480 --> 00:48:11,160 There are two parts to their story 433 00:48:11,160 --> 00:48:13,840 that cameraman, Richard Wollocombe, has wanted to film 434 00:48:13,840 --> 00:48:17,600 since he first came to these islands 25 years ago, 435 00:48:18,800 --> 00:48:21,880 and, on A Perfect Planet, he got his chance. 436 00:48:26,640 --> 00:48:28,760 Driven by powerful currents, 437 00:48:28,760 --> 00:48:33,160 the cold Pacific Ocean slams into Fernandina's shores. 438 00:48:39,720 --> 00:48:43,200 The marine iguanas must brave these waters every day. 439 00:48:48,000 --> 00:48:51,120 Their journey through the big surf is what Richard and the team 440 00:48:51,120 --> 00:48:53,280 are here to film... 441 00:48:53,280 --> 00:48:55,200 ..but from underwater. 442 00:48:56,200 --> 00:48:58,520 It looks fairly benign from the surface here, 443 00:48:58,520 --> 00:49:01,240 but, underneath, it's really shallow, 444 00:49:01,240 --> 00:49:05,200 and there's all these really sharp rocks with lots of jagged edges. 445 00:49:05,200 --> 00:49:07,600 So if we were taken by the wave, 446 00:49:07,600 --> 00:49:10,440 it would cut us up really badly, I think. 447 00:49:15,120 --> 00:49:17,000 Whose idea was this? 448 00:49:17,000 --> 00:49:18,680 Ha-ha, ha-ha. 449 00:49:19,800 --> 00:49:22,000 I'm a glutton for punishment, did you know? 450 00:49:25,920 --> 00:49:29,000 The waves are certainly punishing. 451 00:49:29,960 --> 00:49:32,240 With these dangerous conditions, 452 00:49:32,240 --> 00:49:36,400 extra protection is clearly needed for Richard and dive buddy Rafael. 453 00:49:37,360 --> 00:49:40,040 So what better than surf helmets? 454 00:49:48,440 --> 00:49:52,760 It isn't long before Richard realises what he's up against. 455 00:49:55,760 --> 00:49:58,760 The relentless churning of the water makes it difficult 456 00:49:58,760 --> 00:50:01,240 to stay the right way up... 457 00:50:01,240 --> 00:50:02,840 ..let alone film the iguanas. 458 00:50:08,440 --> 00:50:12,200 In between the waves, the iguanas briefly appear. 459 00:50:16,880 --> 00:50:19,800 But Richard barely has time to line up a shot... 460 00:50:20,760 --> 00:50:23,960 ..before the iguana disappears behind another wave. 461 00:50:31,480 --> 00:50:33,000 In the violent surge, 462 00:50:33,000 --> 00:50:35,960 the iguanas have learned to hang on to the rocks... 463 00:50:37,360 --> 00:50:41,640 ..a trick Richard is quick to copy to avoid being swept away. 464 00:50:43,440 --> 00:50:46,440 That, however, only leaves one hand to film with. 465 00:50:55,400 --> 00:50:58,240 But, with adrenaline carrying him through, 466 00:50:58,240 --> 00:51:02,240 Richard is able to get the perfect shots of iguanas in the surf. 467 00:51:08,520 --> 00:51:13,120 And to achieve that totally unscathed is a great relief. 468 00:51:14,080 --> 00:51:16,800 I don't need to go to the gym for months after that! 469 00:51:19,120 --> 00:51:21,360 Well done, mate. Good job. 470 00:51:24,400 --> 00:51:29,400 On the shore, land iguanas have to battle a very different force. 471 00:51:31,920 --> 00:51:37,520 Each year, they migrate up to the top of Fernandina's active volcano, 472 00:51:37,520 --> 00:51:41,840 a journey of ten days across razor-sharp lava 473 00:51:41,840 --> 00:51:44,960 before descending into its heart to lay their eggs 474 00:51:44,960 --> 00:51:46,800 in the ashy floor. 475 00:51:51,640 --> 00:51:56,000 It's this behaviour Richard and the team plan to film, 476 00:51:56,000 --> 00:51:59,840 and the scale of the expedition is one that's rarely been attempted 477 00:51:59,840 --> 00:52:01,680 in the Galapagos. 478 00:52:06,280 --> 00:52:10,640 To reach the top takes the crew ten gruelling hours. 479 00:52:20,520 --> 00:52:22,960 When they finally arrive on the rim, 480 00:52:22,960 --> 00:52:25,040 the experience doesn't disappoint. 481 00:52:27,320 --> 00:52:29,240 I can't believe it. 482 00:52:29,240 --> 00:52:31,880 It's absolutely awe-inspiring. 483 00:52:34,000 --> 00:52:37,160 I just can't believe the iguanas actually manage 484 00:52:37,160 --> 00:52:41,800 to navigate down these slopes into the bowl of this volcano. 485 00:52:43,480 --> 00:52:46,640 More people have been into space than to the bottom 486 00:52:46,640 --> 00:52:48,800 of Fernandina's crater. 487 00:52:48,800 --> 00:52:52,240 But that is exactly where Richard and the team must go 488 00:52:52,240 --> 00:52:54,880 if they are to film the nesting iguanas. 489 00:52:59,680 --> 00:53:02,640 From their campsite at the edge of the volcano, 490 00:53:02,640 --> 00:53:06,040 it's an extremely dangerous journey down to the crater floor, 491 00:53:06,040 --> 00:53:10,520 and assistant producer Toby wants to be clear with everyone 492 00:53:10,520 --> 00:53:12,440 what is at stake. 493 00:53:30,320 --> 00:53:33,680 There's only one passable route down, 494 00:53:33,680 --> 00:53:37,680 and, as the team enter the lip of the volcano, 495 00:53:37,680 --> 00:53:40,760 the sound of rock fall is all around. 496 00:53:49,640 --> 00:53:53,680 Regular earthquakes make the crater walls very unstable. 497 00:53:58,720 --> 00:54:01,080 Just keeps getting better. 498 00:54:01,080 --> 00:54:05,320 Not far away, some iguanas are making their own descent, 499 00:54:05,320 --> 00:54:07,840 disturbing the loose surface as they go. 500 00:54:19,360 --> 00:54:22,560 If a creature only a sixth the size of a person 501 00:54:22,560 --> 00:54:26,200 can start a deadly avalanche of razor-sharp rocks, 502 00:54:26,200 --> 00:54:28,800 what can a whole film crew do? 503 00:54:35,360 --> 00:54:39,920 It's clear the crew are going to have to be extremely cautious. 504 00:54:44,640 --> 00:54:47,400 On the steepest slopes, the equipment needs to be 505 00:54:47,400 --> 00:54:49,000 lowered with ropes. 506 00:54:57,200 --> 00:55:01,200 With rocks falling all around, the longer they're on the slopes, 507 00:55:01,200 --> 00:55:03,800 the greater the risk of an accident. 508 00:55:07,960 --> 00:55:10,880 But, when one misstep can start an avalanche, 509 00:55:10,880 --> 00:55:12,560 hurrying is impossible. 510 00:55:15,720 --> 00:55:19,400 Finally, the prize of the crater floor is in sight. 511 00:55:19,400 --> 00:55:23,080 Look, just below there is where the iguanas are nesting. 512 00:55:23,080 --> 00:55:27,000 We're very close to it now, about an hour's walk. 513 00:55:27,000 --> 00:55:30,640 All that lies between them is a stretch of loose lava 514 00:55:30,640 --> 00:55:33,960 that has cascaded down the slopes after the last eruption. 515 00:55:47,720 --> 00:55:50,240 We're actually in the crater now, 516 00:55:50,240 --> 00:55:52,960 surrounded by these vertical walls. 517 00:55:54,720 --> 00:55:58,080 I just can't believe that we really made it down here. 518 00:55:59,040 --> 00:56:02,840 Sometimes I doubted that, you know, we would actually make it. 519 00:56:06,080 --> 00:56:10,280 And there they were, iguanas, using the warm volcanic ash 520 00:56:10,280 --> 00:56:12,240 to incubate their eggs. 521 00:56:16,840 --> 00:56:21,760 For Richard, after 25 years living in the Galapagos, 522 00:56:21,760 --> 00:56:25,920 filming this unique behaviour is a lifelong dream come true. 523 00:56:28,280 --> 00:56:31,400 My, God, what an incredible place this is! 524 00:56:31,400 --> 00:56:36,080 It's such a vivid feeling to be constantly challenged 525 00:56:36,080 --> 00:56:38,040 by the forces of nature like that. 526 00:56:39,280 --> 00:56:43,160 But they have to do this every year in order to survive. 527 00:56:43,160 --> 00:56:46,760 I'll never forget, for as long as I live. 528 00:56:46,760 --> 00:56:49,000 What an adventure! What an adventure! 529 00:56:53,200 --> 00:56:54,920 Next time... 530 00:56:54,920 --> 00:56:56,800 ..a new force... 531 00:56:56,800 --> 00:56:58,520 ..humans. 532 00:56:58,520 --> 00:57:00,280 Now so dominant... 533 00:57:01,320 --> 00:57:03,520 ..we're disrupting the forces of nature... 534 00:57:05,480 --> 00:57:09,520 ..and the vital habitats life needs to survive. 535 00:57:11,000 --> 00:57:13,840 This is the most important story... 536 00:57:13,840 --> 00:57:15,760 ..of our time. 537 00:57:15,760 --> 00:57:17,800 Whose future? Our future.