Wetsuit thickness guide
Enter the water temperature and see what to wear in open water - suit, accessories and the safety notes that matter.
The temperature bands
| Water temp | Kit | Notes |
|---|---|---|
| Below 11°C | Full suit + neoprene cap, gloves, boots | Experienced, acclimatised swimmers only. Short swims, never alone. |
| 11-14°C | Full swim wetsuit + neoprene cap, optional gloves/boots | Early/late UK season. Triathlon rules typically make wetsuits mandatory around here. |
| 14-18°C | Full swim wetsuit | The standard UK open water summer band. |
| 18-22°C | Swim wetsuit, optional if you run warm | Comfort and buoyancy still favour the suit for most. |
| 22-24°C | Skin (costume) or swim wetsuit by preference | Many triathlon events start banning wetsuits around here - check rules. |
| Above 24°C | Skin | Overheating in neoprene is the risk now, not cold. |
Race day: wetsuit legality is set by your event's rules (British Triathlon, WTCS, Ironman all differ slightly by distance) - the bands above are training guidance, not a rulebook.
Swim wetsuits are not surf wetsuits
A swim wetsuit is smooth-skinned, buoyant (thicker panels in the legs to lift your hips) and cut for shoulder rotation. A surf suit is none of those things and swims like wet cardboard. If you're buying your first swim wetsuit, get the right kind - then use our wetsuit size finder to get your size right across brands.
Cold water safety, briefly
- Cold shock is the killer, not hypothermia. Enter slowly, control your breathing before swimming off.
- Acclimatise through the season - regular short exposures, not heroics.
- Never swim alone in cold water, use a tow float, and know your exit before you get in.
- Afterdrop is real: you keep cooling after you exit. Dry, dress warm and layered immediately, warm drink, no hot shower straight away.
FAQs
What do UK water temperatures actually look like?
Inland venues roughly: 10-14°C in May, 16-20°C July-August, back to 12-14°C by October. The sea lags a month behind and stays cooler.
Do I need boots and gloves?
Below about 14°C hands and feet lose function first - neoprene gloves and boots extend how long you can swim comfortably and safely.
What about a neoprene cap?
Cheap, small, and one of the most effective upgrades below 15°C - a lot of heat goes through your head, and cold-water headaches are miserable.