LONDON — Intrepid athletes donned snorkels and slithered through slime on Sunday during one of Britain’s quirkiest sporting events: the World Bog Snorkeling Championships.

The annual competition in the tiny town of Llanwrtyd Wells, Wales, sees competitors race to complete two lengths of a 60-yard (55 meter) water-filled trench cut through a peat bog. They can use flippers on their feet, but conventional swimming strokes are banned.

Some contestants accessorized their snorkels, masks and flippers with more flamboyant touches — one carried a giant plastic toad on their head, another had a bathing cap adorned with flowers. Spectators also got in on the fun, with two wearing pink cardboard boxes proclaiming them to be limited edition bog-snorkeling Barbie and Ken.

Competitors at the 35th annual contest were hoping to beat the time of current world record-holder Neil Rutter, who won in 1 minute, 18 seconds in 2018.