Under the sea you can find some very dangerous animals, to. the hammerhead shark has a T-shaped dead and can grow to over 4 metres long. it is quite at home in the warm waters around the world and may attack the creatures it comes across. even humans. the jellyfish seems its opposite. tiny in comparison, the jellyfish has an umbrella-shaped, see-through body with long arms called tentacles. there are about 200 different kinds of jellyfish--varying in sharp, size and color--and 70 of them have sting cells in their tentacles.these can hurt and even kill you kill you if you touch their tentacles. the stingray is another creature that can kill with its sting. it has a flattened body and eyes on the top of its head. the body ends a long tail with spike which can inject venom into enemies. the stingray lurks at the sea bottom and is dangerous to the unwary because it is difficult to see on the sandy floor.