Understanding Neoprene Insulation
Wetsuit thickness is measured in millimeters, and choosing the right number is mostly about one thing: water temperature. Too thin and you'll cut your session short shivering; too thick and you'll be stiff, over-warm, and fighting your own suit. Here's how to match the suit to the water.
A wetsuit doesn't keep water out — it traps a thin layer of water against your skin, which your body warms and the neoprene holds in place. Thicker neoprene insulates better but reduces flexibility, so the goal is the thinnest suit that keeps you comfortable for the water you're actually in.
1. Warm Tropical Waters (80°F / 27°C and up)
In warm tropical water, roughly 80°F and up, many people need nothing more than a rashguard. It won't add real warmth, but it blocks sun and guards against stings and scrapes, and in bath-warm water that's often all you want.
2. Pleasant Temperate Climates (73°F - 79°F / 23°C - 26°C)
From the mid-70s down into the upper 60s, a shorty springsuit or a 2mm full suit hits the sweet spot. You get a little insulation and a lot of mobility, which is ideal for long, active snorkels in pleasant water.
3. Cool Temperate Water (65°F - 72°F / 18°C - 22°C)
Around the mid-60s, step up to a 3mm full suit. This is the workhorse thickness for temperate water — warm enough for extended time in the water without feeling bulky.
4. Cold Open Waters (58°F - 64°F / 14°C - 17°C)
As temperatures drop toward the high 50s, a 5mm suit, often with a hood, becomes the right call, since a surprising amount of body heat is lost through the head.
Wetsuit Fit & Comfort Rules
Fit matters as much as thickness. A wetsuit should be snug everywhere, with no loose pockets at the lower back, knees, or armpits where cold water can flush through and steal your warmth. If it's so tight you can't breathe deeply or raise your arms comfortably, size up. The best suit is one you forget you're wearing — warm enough to stay in, flexible enough to enjoy it.
