(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.

NATURE takes you into the depths of the ocean to discover the most remarkable life still undiscovered on our planet that will certainly be found in the sea.

NATURE takes you into the depths of the ocean to discover the most remarkable life still undiscovered on our planet that will certainly be found in the sea.

NATURE takes you into the depths of the ocean to discover the most remarkable life still undiscovered on our planet that will certainly be found in the sea.

NATURE takes you into the depths of the ocean to discover the most remarkable life still undiscovered on our planet that will certainly be found in the sea.

NATURE takes you into the depths of the ocean to discover the most remarkable life still undiscovered on our planet that will certainly be found in the sea.

NATURE takes you into the depths of the ocean to discover the most remarkable life still undiscovered on our planet that will certainly be found in the sea.