The Maldives are the lowest country in the world--and getting lower, due to rising sea levels. Especially at risk is the island's reef system, the biggest in the Indian Ocean, with over 200 types of coral and thousands of tropical fish species. Witness the race to preserve this marine paradise from the ravages of climate change.

The Belize Barrier Reef is the second-largest coral reef system in the world. Estimated to be nearly 4,000 years old, its waters are home to an immense marine ecosystem. Explore a deep blue wilderness brimming with rare, exotic fish, sea turtles, sharks, and huge green morays.

Palau has set up the world's first shark sanctuary--a California-sized marine zone where hunting these endangered predators is strictly prohibited. Can this tiny island-nation defend against a sophisticated army of poachers? Join the front lines to save one of the ocean's most cherished and endangered predators.

To a marine biologist, any attempt at mapping an oceanic food chain begins and ends with plankton, from tiny bacterial algae to soft-bodied animals such as jellyfish. These microscopic miracles are responsible for producing two-thirds of atmospheric oxygen. Their place at the bottom of the chain has the greatest impact on marine life, whether they're providing nourishment for filter-feeders such as sardines and manta rays or predators like dolphins and sharks.

The coastal waters of Mozambique are the domain of giants, from visiting humpbacks to resident whale sharks. But the tiniest species also play a big role. Brightly colored slugs known as nudibranchs inhabit shallow reefs, estuaries, and mangroves. Of the 200 species here, 90% are newly discovered. Follow the research team as they navigate fickle tides and indiscriminate fishing practices to protect the marine giants of Mozambique--and the tiny creatures that live in their shadow.

Three hundred and seventy miles off the coast of Mexico in the eastern Pacific, the waters surrounding Socorro Island are home to some of the world's largest marine life. Take a deep dive through surging currents and majestic coral reefs with whale sharks, giant manta rays, and more.

Jacques cousteau once called cocos Island "the most beautiful island in the world." beyond its pristine rainforest is a marine wilderness brimming with multicolored fish, enormous sea turtles, and vast schools of sharks.

Forty miles north of Honduras, near the bay Island of Roatan, is a spectacular and pristine preserved coral atoll: the Mesoamerican reef. explore the abundant and diverse marine life, lush vegetation, and magnificent caves of this rare underwater wonder.

Explore the wild blue Caribbean waters of Cozumel, a lush paradise packed with marine surprises. from the spectacular Paso del Cedral coral reef to the world's longest subterranean underwater cave system, go where only the bravest divers dare venture.

Across the 3,000 scattered islands of the Bahamas lie visions of unexpected wonder. Experience its unique natural marvels--from towering pine forests to tangled mangrove swamps, to a mysterious labyrinth of underwater caves.