In the summer here on Maui I usually wear a 3 mil wetsuit and in the winter I wear a 5-7 mil (it is 5 mil in some areas and 7 in the chest area, I think. I don't like to be cold. We don't have may stinging things but I also like the protection. If you are going to be on Maui, I really recommend this operation on Maui's south shore (Kihei) Mike Severn's Diving. I have been diving with them for almost 20 years. Pauline Severns and her crew are absolutely awesome, and the boat does have a bathroom and also the best cinnamon rolls and cookies!