A minimum £3.00 donation will go towards Guernsey Mind and The Sunflower Project.
Check in is from 16:00 at the La Vallette Horseshoe Pool, with the first 50 swimmers starting at 4.30pm, finishing at the Castle Cornet Slipway. Swimmers must be 11 years old.
The oldest swimmers to complete will be awarded the Bill Green Memorial Trophy, and is sponsored by the Louvre Group.
People are allowed to turn up on the day to swim without any registration, but can also email info@guernseyswimming.com to confirm they are taking part.
Any kayakers who wish to help out on the day as escorts are also asked to come forward.