The World Tin Bath Championships tomorrow.
Over 70 competitors from across the world will race a lap of Castletown harbour in a little tin bath.
The winner will be crowned the world champion.
Organiser Dave Collister told us the event has been running for 39 years now.
There's a lot more in store for the thousands of spectators who turn up. In a day out like no other, from 3PM there will be the Manx national snake race, various slapstick stunts by the Castletown Ale Drinkers and intrepid birdmen and women will make attempts at man-powered flight.
There'll be a new event called Jousting baths. Organisers say you have to turn up too see the surprise.
The event raises money for local charities.