Open water: safety, cold water and wetsuits
On this page
Before you get in
RNLI, the UK sea rescue charity, recommends checking the location and its hazards, tides and currents, and the weather forecast, going with a buddy and staying within your limits. If the water is too rough, do not get in. If in doubt, do not go in: getting out is not failure.1
Kit to be seen and to call for help
Also per RNLI: a brightly coloured hat, a tow float, a way to call for help (for example a phone in a waterproof pouch) and a whistle, plus warm clothes and a warm drink for afterwards. A wetsuit helps you stay warm and adds buoyancy.1 The emergency numbers RNLI gives are UK and Ireland ones; 112 is the European emergency number, but always check local guidance.
Cold water
According to RNLI, entering water below 15 °C can seriously impair breathing and movement (cold water shock). If it happens, do not try to swim straight away: the initial effects pass in under a minute; turn onto your back, tilt your head back and float ("Float to Live").12 It explains that cold water triggers an involuntary gasp and raises heart rate and blood pressure, with a risk even for young, healthy people.2 Entering slowly gives the body time to adjust.
The wetsuit
A systematic review of 26 studies reports that the full-body wetsuit allows speed increases between 3.2% and 12.9% over distances from 25 to 1500 m, in several kinds of tests and in open-water events. A long-leg sleeveless model gives an advantage over 400-800 m compared with the full-body one. The authors note that the wetsuit was introduced to prevent hypothermia and that federations limit its thickness and use: rules change by race, so read the event regulations.3 The range is wide and depends on protocol, swimmer and suit: it is not a gain you can claim for yourself.
What we have not verified
- Italian rules and ordinances for bathing and open-water swimming in your area.
- For differences between pool and open water, see the dedicated guide, with study populations and limits kept separate.
- For sighting, see source-described drills and techniques. This page is not a complete guide to group swimming.
What we know and what we do not
The safety guidance is recommendations from rescue bodies, not controlled studies. The wetsuit review is systematic but covers very different protocols. For a race the event regulations apply.
How we reviewed it
Text of two RNLI safety pages and the abstract of a systematic review on wetsuits.
Limits. British bodies, not Italian rules; the wetsuit review covers very different protocols.
Sources
- RNLI. Open water swimming (safety advice). rnli.org (text read)
- RNLI. Cold water shock. rnli.org (text read)
- Gay, Ruiz-Navarro, Cuenca-Fernández, López-Belmonte, Abraldes, Fernandes, Arellano. The Impact of Wetsuit Use on Swimming Performance, Physiology and Biomechanics: A Systematic Review. Physiologia, 2022. DOI (abstract and introduction)
Sources rechecked on 28 October 2026.