www.able.co.nz Captions were made with the support of NZ On Air. Able 2017 An olive ridley turtle. She's resting in the shallows off Costa Rica... ..having swum 1500km to be here. All because the eggs she carries must be laid on dry land. Now she's returned to the very same beach where she hatched ten years ago. She must leave the safety of her marine world... ..and brave the alien world beyond. She's heavily laden, but the future of the next generation of her kind is at stake. All along the beach, in a spectacle that has remained unchanged for millions of years, mother sea turtles emerge from the ocean... ..in their hundreds of thousands. Only those animals that overcome the great challenges of both land and sea can make the most of life here on the coasts. Our shores are places of sudden changes and rich rewards. The Galapagos Islands in the tropical Pacific Ocean. Their barren coastline looks inhospitable, but one group of animals has learned to use it to their advantage. Sea lions. Bachelors. They need to pile on the kilograms, as only the biggest males will attract a female and manage to breed. If these young bulls fail to grow big enough, they will remain exiled on this isolated shoreline. So, one hungry young bull heads out alone. He's on the hunt for big game. Yellowfin tuna. Each weighing 60kg... ..with a top speed of 60km/h. He can't possibly catch one in the open sea. But he has a plan. Ahead lies the entrance to the cove. He herds them towards it... ..into his trap... ..driving them into a dead end. But they give him the slip. He's failed. SEA LION BARKS But there might be another way. Now they head off as a team... ..to round up more tuna... ..driving them back into the cove. The sea lions fan out, channelling the tuna towards the bottleneck. Once again, the tuna hit the dead end. But this time, the young bull doubles back to act as a blocker, sealing off the exit. This time when the shoal tries to escape, he blocks them and drives them back into the next blind alley. The gang can now pick them off one by one. This clever fishing technique, demanding foresight, planning and cooperation, has only ever been seen here in the Galapagos. Each massive fish provides them with five times more protein than a normal day's hunting. Finally, the young bull leaves his post... ..to claim his reward. On a diet of protein-rich tuna, he's well on the way to becoming a full-sized breeding bull. By using this cove, these Galapagos sea lions have made the most of the opportunities that occur where the coast's two worlds meet. Coasts are the most swiftly changing of all ocean habitats because of the tides. Tides are created as the moon's gravity pulls at the sea. As the moon circles our planet, the seas rise and fall, typically twice a day, creating the most constantly dynamic landscapes on Earth. Nowhere else do sea-living creatures face such changeable conditions... ..with the daily risk of drying out and being scorched by the sun. Where the tide retreats across a rocky shore, it can leave behind a temporary oasis. A rock pool. Seemingly, it's a haven of calm. But not for long. reveals unexpected dramas. In rock pools, grazers, scavengers and filter feeders must all make the most of the few short hours before the tide returns. Anemones gulp down anything they can reach... ..though some meals are harder to digest than others. These magical worlds soon become battlegrounds. A deadly predator with five arms and, on the underside, a mouth. The ochre starfish. And it's in search of limpets. For some, there is no escape. It engulfs them. But other limpets have a secret defence. They deploy a slippery shield... ..which allows them to slide to safety. And this limpet has its own personal bodyguard. A scale worm with a nasty nip. The starfish prefers food that doesn't bite back. The limpet carries on, its bodyguard tucked safe under its shell. But there is one creature the limpets have no defence against. A clingfish. It has teeth that can lever under the shell and twist the limpet off like a bottle top. The clingfish then swallows it, shell and all. Rock pool dramas like these last just a few short hours before the tide returns. Every day, the sea becomes land and the land becomes sea... ..bringing new opportunities. A Sally Lightfoot crab. One of thousands of shore crabs just waiting for their moment. Every day, they gather on the tropical shores of Brazil... ..waiting for the tide to go out... ..which exposes their feeding grounds - seaweed-covered rocks 100m from the shore. Getting there is a race against the tide. They leap from rock to rock. These crabs seem to be afraid of the water. And for good reason. The moray eel. The chain moray is a specialist crab hunter. Its blunt teeth can easily grip and crush a crab's shell. It's the crabs' deadliest enemy. But the crabs' feeding grounds are still a long way off. They must press on. Halfway. But their enemy has other ideas. Crossing the land... ..to reset the ambush. To feed, the crabs must keep going. But nowhere is safe. An octopus, also a crab killer. The crabs make a dash for it. Made it! Risking life and limb to graze on these seaweed pastures. But in two hours' time when the tide starts to turn, they will have to run the gauntlet all over again. . You're watching the instant Steve conceived that with a wholesale power price, no dodgy estimates and an easy weekly bill, he'd never find a big hairy surprise in his letter box again. That's enough, Steve. Tides are not the only force to have an impact on the coasts. The greatest waves originate far out to sea and roll in towards the coast, growing as they come. As the shallowing sea floor drags their underside, their crests rise up to 30m high, topple over and break. Many of the biggest surfed waves in the world are formed off Nazare in Portugal. Every day along this coast, the impact of the waves is equivalent to one and a half million tonnes of TNT. Wave power gradually moulds and reshapes our coasts. In some parts of Europe, waves wear away as much as three metres of coastline each year. The rate at which the waves reshape the rock depends on its hardness. Where soft rock lies below hard, dramatic arches are carved. It's an endless assault that gradually sculpts vaulted cathedrals of stone, as here in northern Spain. And wave power creates towering fortresses, like these cliffs in the Arctic, home to tens of thousands of breeding sea birds. The faces of the cliffs are accessible only from the air and have plenty of nooks and crannies for those that can get there. But to feed, sea birds must still master the ocean world beyond. The puffin. He's a fisherman and a father. He has a mate for life. Both share the burden of raising their week-old chick, their puffling, who needs five square meals a day. The parents alternate fishing trips. It's Dad's turn. When fish stocks are low, puffins must fly as much as 50km out to sea to reach the good fishing grounds. Once there, they plunge into another world. Good fishing spots are hard to come by... and they have company. Guillemots. Like the puffin, their wings are short and good for diving. Puffins can hold their breath for over a minute and dive as deep as 40m. A catch! But it's a long way home. After an exhausting round trip of almost 100km, this puffin's nearly made it. But there are pirates on this coast. Arctic skuas. All around, returning parents are being robbed. The skuas' long, raked back wings make them faster and more manoeuvrable. Puffins must choose their moment wisely. A near miss. The last desperate burst of speed... ..and it's made it. Safely home after a three-hour round trip... ..where his patient partner is waiting. Today, their puffling will eat. But where fish numbers are in decline, many puffins now find it hard to get enough food for their chicks. In the changing seas of today, it can be even harder to be a successful puffin parent. Overcoming the challenges of two worlds is seldom easy. One marine creature has virtually abandoned the sea altogether. On a few remote Pacific islands lives the most terrestrial fish on the planet. At the top of this metre-high limestone cliff... ..an eight-centimetre-long blenny has chosen a nest hole. Up here, he can graze on the abundant algae without any competition from seagoing fish. The females are feeding beneath him. He's keen to attract their attention. But they are busy moisturising. Staying damp is essential as they breathe through their skins. To make himself conspicuous, he turns black... ..and flashes his orange fin. He catches her eye. But these Pacific leaping blennies seem afraid of the waves. They're poor swimmers and would be easy prey in the sea. Time to try again. She's tempted. But, once again, distracted by a wave. The male just won't give up. Finally, she's hooked. He makes way... ..so she can enter his cave. And he encourages her to lay her eggs with his seductive dance. He then fertilises them in the safety of his nest. The blenny has given up the sea for a life on land. Others have made an even more successful move, but in a different direction. Penguins have abandoned flying and instead spend most of their lives swimming. Their sleek survival suits of tightly packed feathers are perfect for these freezing waters. Yet they must still come ashore once a year. South Georgia - an island wilderness close to Antarctica. Each spring, its beaches become the busiest on Earth as hundreds of thousands of king penguins return here. They're heading for the colony. But in their way lies the biggest wall of blubber on the planet. Elephant seals. It's the breeding season and the four-tonne bulls are fighting for control of their harems. Best to wait for them to calm down. He can't fly over this barrier so he will have to walk as unobtrusively as possible... ..and hope that sleeping giants will continue to lie. Careful! This could be tricky. A rival bull mounts a challenge. The penguins could be caught in the crossfire. Eight tonnes of blubber collide. The towering beach master is victorious. In the confusion, this penguin slips through. Ahead are 40,000 chicks... ..hungry and overexcited. Not every penguin has a chick to feed. That's not why they're here. There is another reason. There is a trial of endurance that every penguin must face. And it starts with a persistent itch. His survival suit has been worn thin by months of swimming in the rough Southern Ocean. His solution is drastic. Shed all four layers of feathers as quickly as possible. The process is known as a catastrophic moult. Until their feathers regrow, penguins will remain rooted to the spot. Having starved for a month, they're now fully waterproofed and insulated once more... ..lean, hungry and eager to return to a life at sea. Thanks to their waterproof plumage, penguins are able to make the most of both worlds, even in some of the harshest conditions on Earth. The coasts of South Georgia are currently protected by their remoteness. Other coastlines are much more vulnerable. And they are now changing faster than ever before. Two-thirds of our major cities are on our coasts. It's estimated that in the next decade, we can expect 10% of the world's remaining wild shores to be taken over by human development. Yet every year, just off Florida's Palm Beach, an extraordinary spectacle appears almost unnoticed. The biggest gathering of coastal sharks on the planet. Spinners and blacktips. 10,000 of them. Every January, they seek out these warm shallows as a stopover on their migration northwards. Sharks have been gathering here since long before people arrived. But today, they face levels of pollution and habitat degradation as well as fishing pressures that their ancestors would never have experienced. It's no longer enough for coastal creatures to master their own worlds. Now, they must face the many challenges that come from our world, too. Next time, we travel the world to uncover the biggest issues facing the ocean... ..meet the passionate people who've devoted their lives to protecting it and discover what the future holds for our Blue Planet. www.able.co.nz Captions were made with the support of NZ On Air.