The leopard seal is at the top of the food chain in its home in the Antarctic, and this is one predator you don't want to swim with. It is bold, powerful and curious, and it has been known to hunt people, although it usually targets penguins.
In 1985, Scottish explorer Gareth Wood was bitten twice on the leg when a leopard seal tried to drag him off the ice and into the sea, and in 2003 a leopard seal dragged snorkeling biologist Kirsty Brown underwater to her death in Antarctica.
Ian Boyd, director of the Sea Mammal Research Unit in Scotland, said, "There may be a process going on in Antarctica where these animals, because of their growing exposure to man, are becoming a greater danger."
Leopard seals rank alongside killer whales as Antarctica's top predator, according to National Geographic.