Scientific name -- Pelamis pelagicus
Size -- 20'+ long
Diet -- dolphins, human sailors

Sea snakes are a subfamily of the Elapidae, the same family that includes cobras. They are highly venomous pelagic snakes, meaning that they spend almost their entire lives in the open ocean. There are no sea snakes in the Atlantic, though many species live in the Pacific and Indian Oceans. Normal sea snakes can dive to about twenty feet and are capable of removing oxygen from sea water through their skin for short periods of time. Some species also have salt glands to excrete excess salts that are absorbed through the skin. Sea snakes have laterally compressed tails that act as paddles. While their venom is quite toxic, it is delivered in low doses and is rarely fatal to humans.

Giant, spitting sea snakes summoned by God Powers, of course, are a different matter.