Wise move on the skin, Ed...even if not for warmth, a skin will keep you protected against any potential accidental brushes with stinging hydroids, coral or even jellyfish larvae (some of which can be microscopic) floating in the water column that you or he might encounter. I always wear at least a skin, even in the warmest of water for just that reason ('cause I'll tell you one thing- it sure isn't for a fashion statement ).es601:My son claimed he was fine in a 3mm short sleeved shorty but I made him wear a 1mm full skin under it anyways.