Thousands of people around the UK will make a Big Splash this weekend, by swimming to raise money for charity.
A record 645 pools will host fund-raisers swimming a Big Splash Mile for Sport Relief, or one of the traditional Distance Challenges as part of the 25th Swimathon Weekend.
Money raised by Milers will be spent by Comic Relief to help people living incredibly tough lives in the UK, and across the world's poorest countries.
Funds raised by those diving into one of Swimathon's 2.5km or 5km challenges will help Marie Curie Cancer Care to provide free nursing care and support for people with terminal cancer and other illnesses.
At the end of March, comedian Frank Skinner was inspired by Sport Relief to conquer his lifelong fear of water.
Skinner explained: "I really threw myself in at the deep end and faced one of my biggest phobias, swimming, by completing 25 metres for Sport Relief.
"It felt great to challenge myself, which is why I urged everyone to sign up for the Big Splash Mile for Sport Relief."
Olympic silver medallist and World 10km open water swimming champion Keri-anne Payne will start one of the first sessions, at her home pool, Grand Central in Stockport.
Payne said: "Not everyone has time to train for hours every day, but with the Mile you don't have to train too much."
Former England striker and BBC TV presenter Gary Lineker said: "I'm not usually a fan of diving, but if you're going to do it, make sure you do it for a good cause!
"This weekend's Big Splash Mile for Sport Relief is the first chance to do your bit in a pool rather than a road for what has already been an amazing year for the charity.
"I've seen first-hand the enormous good your efforts can do - at a lifesaving learn-to-swim project in Bangladesh."
Event president and Olympic gold medallist Duncan Goodhew added: "We all know that sports such as swimming will enjoy their time in the limelight this year. 2012 also being our 25th Anniversary year, we're delighted to add to the half a million people who have taken part in the event so far, to dive into pools up and down the country.
"These amazing people have raised more than £34m for charity to date - including £6m for Marie Curie Cancer Care alone."