Jonah: Since deckchairs are (at any rate, were) made with a wooden frame, they must float pretty well. A judicious rearrangement of the deckchairs on the Titanic, with the cloth part torn into strips and used to lash many deckchairs together, might have made some very serviceable rafts, and saved many lives.
One of the great truths about life, that used to be–and I hope still is–drummed into the heads of British Army officer cadets, is that very few situations are utterly hopeless. There’s always something you can do, if you are smart & focused enough to think of it. The idiom about the futility of re-arranging deckchairs on the Titanic (Lusitania, whatever) is a discouragement to ingenuity and positive thinking, and I would shun it on those grounds alone.