The Great North Swim weekend gets underway on Windermere later.
Competitors will take on half mile, one mile and two mile courses; as well as more grueling 5k and 10k routes over the next three days.
They'll all be raising money for charity.
This year there's the free Aqua Sphere Lido - where people who aren't taking part can have a go at open water swimming.
Great Swim Director Alex Jackson said, “The Great North Swim is proving to be as popular as ever, with 10,000 expected in Windermere for our ninth event here.
“The new 10k event will provide a new challenge in the original and most iconic of our swims.
“As the largest and most well established swim series in the UK, Great Swim offers an unparalleled open water event experience."