boat vs life raft

boat

noun
  • A craft used for transportation of goods, fishing, racing, recreational cruising, or military use on or in the water, propelled by oars or outboard motor or inboard motor or by wind. 

  • A full house. 

  • One of two possible conformations of cyclohexane rings (the other being chair), shaped roughly like a boat. 

  • A vehicle, utensil, or dish somewhat resembling a boat in shape. 

  • The refugee boats arriving in Australian waters, and by extension, refugees generally. 

verb
  • To travel by boat. 

  • To transport in a boat. 

  • To place in a boat. 

life raft

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. 

How often have the words boat and life raft occurred in a corpus of books? (source: Google Ngram Viewer )