Sea snake - Adapted to a fully aquatic life and unable to move on land, sea snakes are highly venomous.
Box jellyfish - There are at least 51 species of box jellyfish. Some produce extremely potent toxins and have earned the dubious honor of being among the most venomous creatures in the world.
Blue-ringed octopus - One of the most dazzling of mollusks is also recognized as one of the world's deadliest marine animals.
Pufferfish - The majority of pufferfish species are toxic and some are among the most poisonous vertebrates in the world.
Tiger shark - Named for the dark stripes down its body, which resemble a tiger's pattern, this shark species is second only to the great white in recorded fatal attacks on humans.
Lionfish - Lionfish are known for their venomous fin rays, an uncommon feature among reef-dwelling fish along the American East Coast and Caribbean.
Nile crocodile - An apex predator, the Nile crocodile is capable of taking almost any animal within its range, including us.
Great barracuda - A large, predatory fish, the barracuda has been known to attack humans if provoked.
Sea lion - Don't be fooled by the sea lion's cute exterior. When agitated or threatened, these super agile creatures can launch a swift attack.
Water moccasin - The water moccasin, a species of pit viper, is the world's only semi-aquatic viper, and is native to the southeastern United States.