In three decades, the waters around the remote village of Cabo Pulmo have gone from wildly biodiverse, to barren, to a bountiful and pristine haven for mighty sharks and flying rays once again. See how local fishermen ultimately turned back the clock, restoring one of the world's most majestic coral reefs.

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.

In Palau, the local economy relies on ecotourism that's sustained by strong legal support. Shark hunting is banned, giant manta rays are protected by law, and tireless efforts are made to combat the acidification an ocean ecosystem housing coral reefs. But can ambitious conservation keep pace with the scale of man-made devastation?

The vibrant reef ecosystem of Raja Ampat, off the coast of Indonesia, is home to a conservation sanctuary twice the size of Singapore. It's one of the few places on Earth where two different species of manta ray live side by side. Join a dedicated team of conservationists as they track these mysterious creatures to safeguard their future.

Indonesia's marine rainforests are under threat, and rising sea temperatures and destructive fishing practices have taken a toll. However, conservation initiatives in hundreds of protected marine zones have given hope to the giant manta rays, 300 species of coral, and six of the world's seven sea turtle species that call this ecosystem home.

Beneath Indonesia's coral reef, tiny creatures have made the murky seabed their home. Here, you'll find shrimps that kill with a whip-fast punch, toxic nudibranch sea slugs, and six of the nine species of the world's walking sharks. Dive into the depths of this unlikely ocean ecosystem.

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 Pacific coast of Costa Rica is home to an astonishing 3.5% of all marine species in the world. Helping keep things in check is the region's apex predator, the hammerhead shark, whose dwindling numbers present a major threat to the health of the ecosystem. Witness the efforts to keep this mighty creature alive.