Well if you have not read the thread on the main crappie fishing forum yet, the thread called, "I fell out of the boat today and..." you should. He is very lucky to be back on crappie.com telling his story with the extremely cold water temps we have out right now. I was reading 41 degree water saturday and you just don't function for long once your in that water temperature. Definately if you fish alone, you need to wear your life jackets.
Attached below is a link to a video about the effects of cold water on the body. Pretty interesting and informative. You may need a fast connection to watch it though. Basically it teaches you that you have a 500 percent higher chance of drowning when the temp is under 59 degrees and right now it's 41. I took one finger and held it in the water for a good many seconds saturday and you just cant imagine how cold that water is now, till you actually feel it. Please be careful while on the water in these temps. Take a friend if you can :D

YouTube - Cold Water Boot Camp