Indian Ocean: the SeychellesNorbert Wu/Minden Picture/National Geographic Creative
A pair of spotted porcelain crabs perch on the slippery edge of a giant anemone. They have a mutualistic relationship: The crabs keep the anemone clean, while the anemone and its poisonous tentacles act as deadly bouncers to keep predators away from the petite, 1.4-inch-long crustaceans. Check out these rare photos of ocean's invertebrates.
North Pacific Ocean: Honshu, JapanBrian Skerry
The yellow goby fish, also known as an Okinawa goby, likes to live in coral reefs, but here it has taken shelter in a discarded soda can. The teeny, 1.5-inch-long fish is endowed with a powerful biological defense against attackers: It makes itself unpleasant to eat by secreting a bitter, poisonous mucus. Ever wonder how much sleep each animals needs. Here are the numbers for the cutest ones.
Arctic Ocean: Nunavut, CanadaPaul Nicklen/National Geographic Creative
Drifting pack ice enables a walrus to remain near a favored foraging area, a clam bed in Foxe Basin. North of Hudson Bay, Foxe Basin is home to Canada's largest walrus population: around 6,000. These unexpected animal heroes saved the day.
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South Pacific Ocean: Shark Reef, FijiMattias Klum/National Geographic Creative
Clinging to its fast-moving host, a remora finds safe transport aboard a whitetip reef shark. Not considered dangerous to humans, the shark is relatively small, maxing out at five feet. The relationship between the two creatures is one that's win-win: Remoras feed on parasites and keep the sharks clean; the sharks provide a swift ride, protection, and leftover food. These animals are a lot smarter than you may think.
Arctic Ocean: Spitsbergen, NorwayRalph Lee Hopkins/NGC
A polar bear and her cubs walk along the pack ice near the coast of Spitsbergen, the largest island in the Svalbard Archipelago—and in Norway. Polar bears are the beloved symbol of the island, which has a human population of 2,642. If you want a good laugh read up on these funny animal jokes.
South Pacific Ocean: Great Barrier Reef, AustraliaDavid Doubilet/National Geographic Creative
A marine scientist dives above a garden of corals of the Great Detached Reef, the far northern section of the Great Barrier Reef. Since the 1950s, nearly half of the world's coral reefs have disappeared or are in a state of sharp decline.
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See the splendors of the sea
"Every cubic mile [of the ocean] is a thriving metropolis of large, medium, and exquisitely small lives interacting in ways that make Earth more hospitable for life as we know it," writes pioneering oceanographer Sylvia A. Earle in the new National Geographic book, Blue Hope: Exploring and Caring for Earth's Magnificent Ocean. In the book, you can find all of the preceding photos, discover more fascinating, fantastical creatures, and learn about the state of our seas.