A wetsuit is the most effective piece of sun protection most watersports people own, and almost nobody thinks of it that way. Neoprene is thick, opaque and completely impervious to ultraviolet. Whatever it covers is not merely protected, it is removed from the problem entirely, for the whole session, with no application quantity, no reapplication and no degradation.
That should be the end of the story. It is not, because a wetsuit has edges, and every edge is a failure line.
The conditions, set out plainly
Wetsuit use, any discipline
Conditions block- UV load
- Whatever the discipline and the day give. The suit does not change the dose, only its distribution.
- Water exposure
- By definition.
- Sweat
- High inside the suit, irrelevant to protection because the neoprene is opaque.
- Friction
- Very high at every seal and cuff. This is the defining feature.
- Typical duration
- As long as the session.
- What fails first
- The band of skin immediately outside each seal, in every case, every time.
- Protection strategy
- No product under the suit. A generous, high cling application to the four edge zones before the suit goes on, reapplied at every exit, plus a decision about whether a rash vest or a hood removes the problem entirely.
The four edges
1. The neck seal
The most reliable failure in the whole sport. The seal sits on the skin and moves against it constantly, especially in swimming and surfing where the head turns on every stroke. It abrades the film off a band of skin at the throat and the back of the neck, and that band is presented directly to the sun. Wetsuit users get a sunburn ring, and it is one of the more uncomfortable places to have one.
2. The wrist cuffs
The backs of the hands sit immediately outside the cuff, take direct sun for the entire session, are wet the whole time, and get abraded by the cuff edge on every arm movement. Hands are also the part of the body people apply to last, and the part most thoroughly washed at the end.
3. The ankle cuffs
Less exposed in swimming, more exposed in surfing, kayaking and anything where the feet are out of the water. The tops of the feet burn badly and often.
4. The line where a shorty ends
Mid thigh or mid upper arm, straight across, in a place with no natural sun exposure and therefore no adaptation. The burn line matches the neoprene exactly, which is what makes it so recognisable.
Why you should not apply under the suit
Three reasons. First, it does nothing, because neoprene blocks ultraviolet completely. Second, some formulations can interact with the material or with the suit's inner lining over time, and a suit is expensive. Third, and most practically, applying under the suit makes it far harder to get on and wastes product that is doing no work.
Apply to the edges and to whatever is outside the suit, generously, and stop there.
The reapplication clock
Reapplication clock: Any wetsuit session
The wetsuit clock is not about the whole body, it is about four narrow bands. Mechanism only.
The problem after the session
Peeling a wetsuit is a slow, awkward, public activity that takes place in a car park in full sun, with wet skin and whatever remains of any film comprehensively removed by the neoprene on the way past. Then there is the getting changed, the packing up, the standing around talking. For a lot of people this is thirty to forty minutes of unprotected exposure at the end of a long session, on skin that has been in cold water and is not sending any useful signals.
Put a t-shirt and a hat in the boot next to the towel, and reapply after changing if you are going to be outside afterwards. It is the least glamorous advice on this site and one of the most useful.
The alternatives that remove the problem
- A hood or a thermal cap covers the neck seal zone completely and is normal winter kit anyway.
- A rash vest under or over the suit can extend coverage past a shorty line.
- A long sleeved suit rather than a shorty in strong sun, which is counterintuitive in warm water but effective.
- Neoprene gloves and boots remove the hand and foot problem entirely.
The general principle throughout this guide is that textile beats film wherever textile is practical, and a wetsuit is textile taken to its logical conclusion. See our note on UPF clothing for how fabric protection is rated.
What the label will and will not tell you
Water resistant, 40 minutes
What it certifies
On a pack made for the United States market, that the product was assessed under the Food and Drug Administration monograph procedure and retained its labelled sun protection factor after a specified period of water immersion. The United States requires the duration to be stated in minutes on the label, which makes the claim unusually explicit about its own limits.
What it does not
It does not mean protection ends at forty one minutes, nor that it is intact at forty. It is a testing threshold, not a countdown. And, as with the UK and EU procedure, no part of it involves abrasion, which is what a wetsuit seal does.
The United States convention of stating water resistance in minutes is instructive precisely because it is explicit. A UK or EU pack expresses the same idea as a category, and the underlying procedures are not identical, which is one of several reasons a pack bought abroad does not mean what a British reader assumes. Our note on buying sunscreen abroad works through it.
Hire suits and borrowed kit
A hire suit rarely fits as well as your own, which usually means looser seals and more movement against the skin. Expect more abrasion at the neck and cuffs, and apply accordingly.
What is not verifiable
We cannot tell you how quickly a seal abrades a particular formulation, because no published procedure tests it and we run no tests. That gap is real and worth stating plainly rather than filling with a guess. What is verifiable is the geometry: you know exactly where your suit ends, and you can see the burn line afterwards if you got it wrong.
After the season
The wetsuit pattern, throat, wrists, ankles, thigh line, is a useful thing to know about your own skin, because it tells you where to look. The NHS publishes sun safety guidance and we would rather you took an unremarkable mark to a GP than left a changing one. We give no diagnostic guidance.