The 125-mile event takes place over the Easter holiday
The 125-mile Devizes to Westminster canoe race has entered its second day with the start of the non-stop event.
The senior race - in which kayakers paddle non-stop through the night - is said to test competitors to the limit of mental and physical endurance.
The juniors' race started on the Kennet and Avon canal on Friday and is due to finish at Westminster bridge on Monday.
Double Olympic gold medallist rower James Cracknell, who is competing, said he was always up for a new challenge.
"When you do one sport quite seriously, it sort of precludes you from doing anything else and there are so many great things to do," he said.
"I've been lucky to do some long distance things abroad but there's loads of good things to do in this country and this is something that, when I used to train a lot at Henley, you'd watch these guys come through at all hours of the weekend, I'd think it's something that should be attempted.
"Obviously switching from rowing to canoeing is not really done, but for a weekend it's alright."
More than 600 competitors are taking part in this year's race.