The Collaborative International Dictionary
Sea snake
Sea snake \Sea" snake`\ (Zo["o]l.) Any one of many species of venomous aquatic snakes of the family Hydrophid[ae], having a flattened tail and living entirely in the sea, especially in the warmer parts of the Indian and Pacific Oceans. They feed upon fishes, and are mostly of moderate size, but some species become eight or ten feet long and four inches broad.
Wiktionary
sea snake
n. Any of several snakes, of the subfamily ''(taxlink Hydrophiinae subfamily noshow=1)'', that live in the waters of the Pacific and Indian Oceans.
WordNet
sea snake
n. any of numerous venomous aquatic viviparous snakes having a fin-like tail; of warm littoral seas; feed on fish which they immobilize with quick-acting venom