life raft

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

• noun A raft usually made of inflatable material or wood and used in an emergency on large bodies of water.

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

• noun A usually inflatable raft carried aboard a ship or airplane, used to save lives in case the vessel has to be abandoned in an emergency on the sea.

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

• noun a raft to use if a ship must be abandoned in an emergency