Real men don't wear togs

If the passengers on this morning's high-speed ferry from Holyhead to Dn Laoghaire care to glance to port as they approach the Irish shore, they may catch a glimpse of a small, round tower - looking like an only slightly overgrown escapee from the corner square of a chess board. It acts as a beacon for bathers drawn to the most absurd swimming-pool in the British Isles.

I suspect that most occasional sea bathers share the following criteria for a decent dip: the water should be clear and warm; getting in and out should not require any great effort and/or contortion; there should be a private place to change, preferably with a hot shower.

The Forty Foot Pool meets none of these conditions, yet it is as popular as it is ridiculous. If you wander along the shore just south of Dn Laoghaire expecting to find a gently shelving circular pool with a diameter of approximately 40ft, filled with sea-water that has at least lost its chill to the tentative sun, you will be as disappointed as drizzle.

The costume-clutching novice is first greeted with some serious signs. "Gentlemen's Bathing Place" instructs a notice which has evidently been there for decades, ground down by the fine, salty mist that represents fall-out from the pool. A less permanent sign perched close to an old tin roof may or may not be present, depending on the time of day you attend: "Togs must be worn".

The Forty Foot Pool is a subject of much controversy in Dublin society, polite or otherwise. Its name has no correlation with its dimension, instead being a reference to the 40th Foot Regiment of the British Army, which for a time was stationed at the Martello Tower. The troops performed their ablutions naked, creating a precedent followed by local civilians. Men only, mind.

Gradually a notion permeated even the most conservative corners of Catholic Ireland: that women should be permitted equality of access to recreational facilities such as the Forty Foot Pool. The gentlemen bathers were shocked at the idea of women observing, let alone partaking in, their naked rituals. So a solution was devised: from dawn to 9am togs need not be worn; beyond that, the sign goes up.

What, you wonder as you wander down past the open-plan shed that serves as the (un-) dressing room, was all the fuss about? The "pool" opens up on to the Irish Sea in all its grot. Rocks seem to jostle you as you pick your way unsteadily towards the murky water, the same troubled grey as the leaden midsummer skies. A few betogged gentlemen bathers dive casually from some of the bigger boulders into the swirling, gloomy sea that collides frequently and violently with the shore.

Your turn. A precarious handrail invites you to descend into the water, but gradual immersion is not a realistic option. Yet after trepidation has ratcheted to a maximum, the plunge is bracing rather than beastly. The Irish Sea doesn't exactly caress you, but neither does it fling you straight back to the rocks. A few tacks, a gulp or two of worryingly tangy water and you have passed the Forty Foot test.

Now you have the confidence to turn up on Christmas Day, when the location is packed with frosty forty-footers. But perhaps you have suffered enough, and deserve a touristic antidote. Remember that tower? Once the residence of James Joyce, it served as location for the opening scene of Ulysses and now houses the James Joyce Museum. The writer's deathmask stares blankly, curiously offsetting the dense prose of his letters and first editions. The view from the roof takes in Howth, on the far side of Dublin Bay, as well as the strident Wicklow Hills. And, down at the shore, some shameless, shivering show-offs.

Simon Calder takes a plunge into the Forty Foot Pool for `The Travel Show' on BBC2 at 8.30pm on 21 July