I wear a 3mm shorty over a dive skin. When I get back in the boat I remove the top of my wetsuit and dive skin, even in May, otherwise evaporation in the wind caused by the boat movement will chill me pretty rapidly and I will be cold on the second dive.I normally use just a shorty with hood. This year I have been happy wearing full 5mm and hood. Been a windy winter here so you cool down once you are on the boat. Its warming up now....