When we were cruising the Sea of Cotez during the summer, the sea water temp was over 95 deg. F. BUT, about 10 feet down it dropped by more than 10 to 15 degrees.
I would drop the pickup down as deep as I could and was down the deck with the colder water. Like an AC system! It was GREAT.
I also have a strainer on the pickup hose. I used a spare collar zinc as my weight.
Greg