1) Family hydrophidae 2) Reptile family 3) Sea snakes 
A family of sea snakes comprising about 50 species with flattened oar-like tails used as sculls. They are found mostly in the coastal waters of south asia and Australia. The largest reach a length of almost 9 feet but most species are only about a third as long. They are all venomous. (goin, goin, and zug, introduction to herpetology, 3d ed, pp331-...
[n] - sea snakes
family Hydrophidae noun sea snakes