Sea snakes are exceptionally venomous. When I was in the US Navy sailing on the Indian Ocean, we would pass over huge clouds of sea snakes. If someone were to fall overboard and get bit by one of them, they'd probably be dead by the time we were able to turn about. Luckily, the sea snake has an extremely small mouth, so it can only bite you on thin parts of your body, such as the webbing between your fingers and your ear lobes.