It's all what you are use to, was just diving last week in the Philippines water temp at 100ft down was 29C everyone was looking at me like I'm crazy putting on only polyeflin shorts and a short sleeve rash guard. They all had 3 and 5mm, then again one month ago was diving in Tahoe in a 1mm full polyeflin suit and hood, temp was 15 to 15 C. got kinda cold after 10 minutes, but not unbearable.