Went fishing at my usual NRD pond here in Nebraska Thursday night. I can't keep the cats alive on the stringer. I go through the bottom lip and the stringer will put them down to about 8' of water. I am catching them in about 2-3' of water. Don't know what the actual water surface temp is, but is warm. In a matter of about 20 minutes these fish are dead. I wold think that 8' would be cool enough, if they are feeding/working the shallows. These fish are ranging 3 to 12 pds channels.