Wonder what it would be like to swim with billfish like Rick Rosenthal in Superfish? This field guide should give you sense of these creatures' amazing size.

(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.

High concentrations of mercury, a neurotoxin that can damage developing brains in fetuses, are found in some kinds of popular fish such as albacore tuna.