Every year, hundreds of people descend on the Welsh town of Llanwrtyd Wells to take part in the World Bog Snorkelling Championships.
Prizes are awarded to the fastest swimmers to cross the 55-metre-long trench in the Waen Rhydd bog, without once emerging, and fancy dress is optional but encouraged.
Reigning world bog snorkelling champion Neil Rutter tells Nights about the event.
(One of Nights host Mark Leishman's favourite interviews of 2023)