Open water swimming has grown dramatically in popularity — from organized lake swims and ocean marathons to casual wild swimming in rivers, reservoirs, and coastal waters. It is one of the most rewarding forms of exercise and one of the most UV-intense.
Unlike pool swimming, open water means no roof, no shade structure, and often no way to exit the water and reapply sunscreen during a session. UV exposure accumulates continuously. The scalp, the back of the neck, and the shoulders face directly upward for the entire duration of a swim.
Why Open Water Swimming Is High UV Risk
Several factors combine to make open water swimming particularly high risk for UV exposure:
- No shade. Lakes, oceans, and rivers offer no overhead protection from UV.
- Water reflection. Water reflects up to 50% of UV radiation back at exposed skin from below, effectively doubling the UV dose at the surface.
- Extended sessions. Open water swims often last 30 minutes to several hours — far longer than a typical sunscreen application is effective for.
- No reapplication possible. You cannot stop mid-swim to reapply sunscreen. Whatever protection you start with is what you have for the entire session.
- Peak hours. Many open water swimming clubs and events take place in morning and midday sessions when UV is highest.
The Solution: UPF Clothing From the Start
The only sun protection that lasts the full duration of an open water swim is UPF clothing. Unlike sunscreen, it does not wash off, does not require reapplication, and does not diminish with time in the water.
For open water swimmers, the two most important items are a UPF swim hat for scalp and neck coverage and a UPF swim shirt for shoulder and torso coverage.
Best UPF Gear for Open Water Swimmers
Swim Hat
The Classic Nammu is the most popular choice for open water swimmers — streamlined, secure at swimming pace, and available in bright colors that improve visibility in the water. The secure fit holds through flip turns, waves, and sustained front crawl.
For swimmers who also snorkel on the same trips, the EX UV Pro with Ear Flap adds ear coverage and additional neck protection.
Swim Shirt
A UPF 50+ swim shirt or hoodie provides full torso and arm coverage for the duration of the swim. The Nammu hoodie swim shirt adds hood coverage for the back of the head — particularly useful for cold-water swimmers who prefer additional head coverage.
UV Sun Wrap for Before and After
A UV sun wrap is ideal for the time spent waiting to enter the water, during post-swim recovery on the bank or beach, and for the journey home when skin may still be warm and sensitive.
Practical Tips for Open Water Swimmers
- Wear UPF from arrival, not just in the water. UV exposure starts the moment you arrive at the swim location — often in full sun on the bank or beach.
- Apply mineral sunscreen to exposed skin before entering. Face, hands, and any areas not covered by UPF clothing.
- Check the UV index. On high UV days (8+), consider earlier or later sessions.
- Bright colors improve safety. Nammu hats are available in bright, high-visibility colors — important for being seen by boats and other water users during open water swims.
- Rinse and moisturise after every swim. Freshwater and saltwater both affect the skin’s moisture barrier — rehydrating skin after swimming is as important as protecting it during.
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