It’s all about water temp, dude. In chilly zones (below 58°F/14°C), you’ll want a 4/3mm or even a 5/4mm with boots, gloves, and a hood. For most temperate climates, a 3/2mm is the go-to year-round suit. In tropical or summer water, a 2mm spring suit or just boardshorts and a rashguard will do. Being too cold is a session killer, so when in doubt, go a mm thicker!