Yes, in some cases the "warmer" water is in the top few feet & fish will seek such water.

And I've caught Crappie in 40* water, right next to the bank in <3fow (fishing from the western bank, shortly after sunrise, over and next to a large deadfall that extended from the bank out into 25fow). Fish were ususally 8' down over the treetop & deep water, but some were right next to the tree trunk at the rocky shoreline. Air temps were in the 30's (Jan).