What to Wear Under a Wetsuit
A wetsuit works by sealing a thin layer of water against you. That single fact decides what should be underneath it, and it rules out most of what people wear.
The Sea Swimmer's Case for the Swim Brief
Best swimwear for cold water sea swimming: why the regulars at the Forty Foot all wear swim briefs, and how a two second change keeps you warm.
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Stand at the Forty Foot in Dún Laoghaire on any winter morning and watch who gets in. The once-a-year crowd arrive in board shorts. The regulars, the ones who swim every day of the year including Christmas, are almost all in the same thing: a small, unglamorous, entirely practical swim brief.
This is not a coincidence, and it's not a fashion choice. Cold-water swimming is the most honest product test swimwear ever faces, and the brief wins it on every line. Here's the case, from the people who take the test daily.
The numbers behind the boom
First, the context. Sea and open-water swimming stopped being a niche eccentricity during the pandemic and never went back. In Britain, the number of regular open-water swimmers more than doubled in seven years, from 266,000 to over 540,000. In Ireland, swimming is now the second most-participated sport in the country, with around 350,000 regular swimmers and every tidal pool from Sandycove to Salthill busier than it has been in living memory.
That's several hundred thousand new people learning, through direct experience, what competitive swimmers always knew.
The cold-water arguments
Wet fabric is cold fabric. This is the big one. Every square centimetre of wet cloth against your skin after a cold swim is actively chilling you while you fumble for the towel. Board shorts hold litres of freezing seawater against your thighs; a brief holds almost nothing. On a December morning that difference isn't comfort, it's how long your hands work. The same physics decides what goes under a wetsuit, where an absorbent layer becomes a cold sponge the suit has to fight all session. What to Wear Under a Wetsuit
The change is the whole battle. Sea swimmers change outdoors, fast, under a towel or a changing robe, often in wind. A brief comes off in two seconds and wrings out in one squeeze. It's dry before your coffee's poured. Shorts are still dripping in the footwell of the car at lunchtime.
Nothing drags in the water. Loose shorts balloon and drag with every kick. For anyone actually swimming rather than dipping, the brief is simply the correct tool, which is why nobody at any swim club anywhere trains in board shorts. The Case for Briefs: Why They Should Be Every Man's Default
The pocket of the changing robe. The entire kit for a year-round swimmer is: brief, towel, robe, hat, flask. The brief version of that kit fits in a coat pocket. There's a reason the dryrobe-and-brief combination has become the unofficial uniform of the Irish coastline.
What the regulars wear
The standard issue: a plain, durable, chlorine-and-salt-proof brief from the specialists. This is the pair you'll see at every tidal pool in the country. Speedo Endurance swim brief · Arena training swim brief
The character pair: sea-swimming culture is sociable, and a loud printed pair has become part of the fun. The Australians run this category. Budgy Smuggler printed swim brief Break Out the Budgy Smugglers: The Aussie BBQ Guide to Swim Briefs
The trunk-cut compromise: a square-leg trunk gives you the same low-drag, quick-dry physics with a few more centimetres of coverage, and it's a completely respectable way in. square-leg swim trunk
The social physics of the slipway
One more thing the sea teaches. At the water's edge, the usual body anxieties evaporate with startling speed, because everyone is too cold, too exhilarated and too busy to perform. Sixty-year-olds in briefs chat to twenty-year-olds in briefs and nobody has ever once cared. The sea swimming boom has quietly built exactly the judgment-free changing room that the gym never managed. If the locker-room fear is what's kept you out of a swim brief, start at the slipway. It's the friendliest venue in the whole campaign. The Locker Room Question: Getting Over the Fear of Being Seen in Briefs
Cold water clarifies everything. It'll clarify your swimwear too.