Guess what I was wondering- Is it the evaporation of the water that would make one get so cold so fast? If so, would wrapping myself in the garbage bag stop the evaporation, and help me stay warm long enough for fire?
Or would the water in the clothes conduct too much heat away anyway?
I think it is a 3-part problem
1) You have to heat the water next to your skin and the water in your clothes. Water has a very high heat capacity, requiring lots of energy to raise the temperature of said water.
2) Evaporation. The colder, the more pronounced effect. Wind increases the evaporation a lot.
3) I haven't the data to back it up, but my gut reaction is that heat conduction through the wet clothes is the least of your worries.
Anyway, I second the procedure outlined above by several others: Strip down, wring semi-dry, put back on, add vapor barrier. Then think about your options about evacuating, building a fire, bivuacking or just continuing your merry way, depending on circumstances.
I'm not sure of the scientific explanation, but I can tell you from personal experience that certain fabrics remain "survivable" warm when they're soaking wet.
Yes. Fleece is amazing stuff, but I really don't like it when it's wet. Wring it fairly dry, put it on. I am sure there must be more synthetic fibres with similar properties out there.
Wool is even more amazing, and my #1 choice for outdoor underlayer (with the exception of my cotton boxer shorts, which has been nowhere near of killing me - yet). For the middle and insulation layer I mix wool and fleece, depending on circumstances.