I have a walleye type boat which has a hugh livewell. First thing I do after getting on the water is fill up the livewell with clean water and drop a few frozen gatorade bottles in. Once they melt I switch 'em out with a few ice packs and I'll have the water inside the livewell a good 10*-15* cooler than the lake surface water. Crappie swim around frisky & healthy until I reach home and drain the livewell.