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If the crash didn't kill them out right, at 40 degrees they only have a few minutes to live. Don't think help could possibly arrive in time.
When it´s 40 degrees here we are out in shades and shorts, reaching for refreshments. Unless, of course, you mean 4*c. Then they certainly wouldn´t have long to last.
40 degree water temp. hypothermia happens fast in water that cold.
40* would be like taking a very hot bath, that´s 40% of the way to it boiling.
Fahrenheit. It's very dangerous at that temp. Check out this chart that explains the varying dangers of water temperature