Do you have special memories of time you've spent at the ocean -- or in it? Have you had a close encounter with marine life? NATURE wants to know about it.

(Airs Sunday, August 29) Marine biologist Rick Rosenthal set out to capture on film the biggest, fastest, most dangerous gamefish in the sea -- the ancient creatures known as billfish.

Giant-wave surfers from around the world couldn't walk away from the largest waves ever recorded.

All waves share certain characteristics. See inside giant waves and find out how they work with this interactive feature.

Krill, which are small, shrimp-like creatures, represent the very cornerstone of the Antarctic ecosystem.

The world's nearly 300 turtle species have a remarkable range of behaviors, from wood turtles that stomp the ground to attract worms, to sea turtles that travel thousands of miles to lay eggs.

TOOTHWALKERS presents extremely rare under-the-ice footage that reveals a complex and potentially dangerous side to this huge and often mysterious mammal.

TOOTHWALKERS presents extremely rare under-the-ice footage that reveals a complex and potentially dangerous side to this huge and often mysterious mammal.

TOOTHWALKERS presents extremely rare under-the-ice footage that reveals a complex and potentially dangerous side to this huge and often mysterious mammal.

TOOTHWALKERS presents extremely rare under-the-ice footage that reveals a complex and potentially dangerous side to this huge and often mysterious mammal.