sea snake

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various venomous tropical snakes of the family Hydrophidae that are adapted to living in the sea, especially in the Pacific and Indian oceans, and that bear live offspring.

Century Dictionary and Cyclopedia

1. n. A sea-serpent, in any sense.

Wiktionary

1. n. Any of several snakes, of the family Hydrophiidae, that live in the waters of the Pacific and Indian Oceans.

GNU Webster's 1913

1. Any one of many species of venomous aquatic snakes of the family Hydrophidæ, 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.

WordNet 3.0

1. 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