Forty Foot — an open-sea bathing place in Sandycove, at one time "gentlemen only", but now welcoming to all.
The cove, where most of the swimming and jumping is done, forms a deep sea-water inlet (though by no means is it forty feet deep). High walls and the rocky shore conceal it from innocent eyes, so that a certain relaxation of the usual rules has always applied with regards undressing and dressing again. (The Forty Foot was long the favourite, and perhaps sole, resort of Dublin's male naturists.) Summer frivolity and winter shivers, these equally are disdained by the "regulars", those seasoned swimmers who seem to push the sea out of the way to get in.
Nobody really knows where the name came from. Doyler's suggestion in the novel that it comes from the Fortieth Foot regiment seems reasonable – save there are no records of that regiment being stationed in Ireland at an appropriate time.
Buck Mulligan, in Joyce's Ulysses, takes his morning dip here, in the "snotgreen", the "scrotumtightening" sea. It also features in L.A.G Strong's novels, The Garden, 1931 and The Sea Wall (London: Gollancz 1933).
The swimming area is formed on the rocky skirts of a long-disused battery. This battery or fort, constructed about 1810 (along with the nearby Martello), occupies much of the granite outcrop that forms Sandycove Point. Its curving hewn-granite walls screen the swimming area from public view. At one time it held a garrison of 36 men, and it's thought these soldiers were the first to use the foreshore roundabouts for bathing.
In 1880, regular swimmers formed the Sandycove Bathers' Association. Paths were laid out and steps cut in the rock, ladders installed and, at one time, diving boards and rafts. Competitions and gala days were frequent. Nowadays it's the Christmas Day Swim that attracts most outside attention.
A 1947 editorial in the Dublin Evening Herald observed:
The editorial then went on to remark upon the recent case of two young men who had been arrested for sunbathing together naked:
The case against the two young men was dismissed.
Archived copy (at Internet Archive) of: FortyFoot.org
Wikipedia: Forty Foot
Forty Foot Christmas Swim
Winter Waves
Swell Day at Forty Foot