sea snake

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various venomous aquatic snakes of the family Elapidae (or Hydrophiidae) that inhabit tropical waters of the Pacific and Indian Oceans and that bear live offspring.

from The Century Dictionary.

• noun A sea-serpent, in any sense.

from the GNU version of the Collaborative International Dictionary of English.

• (Zoöl.) 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

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

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun 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