The 170 contestants took part wearing everything from flippers and snorkels to pyjamas and camouflage. One competitor even wore an ironing board.
Winner Conor Murphy, 23, from Leicester, came in at 1 min 38.9 sec at the event in Llanwrtyd Wells, Powys.
Organiser Sheelagh Tompkins said: “I think people have been inspired by the Olympics. There are lots of serious competitors.”