The 30 Bays in 30 Days challenge gets underway across the Channel Islands today (1 July).
The fundraiser takes place throughout the month of July and encourages islanders to swim "before work, at lunchtime, during the day, after work, and by moonlight" to raise money for charity.
Participants can sign up online and are to pay £12 in Jersey and £15 in Guernsey to register for the challenge - they are then encouraged to collect sponsorship for the following charities:
National Trust Jersey
Jersey Hospice Care
Les Bourgs Hospice, Guernsey
It costs £6 for under 18s in Jersey and £5 in Guernsey.
Guernsey's event launches with an organised swim in Vazon Bay at 6.30pm on 1 July and culminates in a second mass swim in Cobo Bay on Friday 30 July.
For the first time, five Alderney bays are being included in Guernsey's challenge.