A group of Royal Engineers will take on one of the toughest canoe races in the world this Easter.
The Devizes to Westminster International Canoe Race is 125 miles long.
It's a non-stop race with many obstacles along the way.
Often referred to as the 'Mount Everest of canoe races', Lord Paddy Ashdown tried it during his time as a Royal Marine, saying afterwards:
"It was crippling. We took 25 hours to finish the course, and I can only think of one person in history who has spent a worst Easter".
There are 77 locks and weirs along the course to keep canoeists on their toes (or fingers).
The first 52 miles run along the Kennet and Avon Canal, but at Reading the course runs into the River Thames.
Once they reach Teddington, the tides must be battled all the way to the end of the course at Westminster, which might explain why the course is so gruelling.
Corporal Chris Lay, of the Royal Engineers, has done the course before - and will be doing so again:
"Ideally, I want to get under 20 hours, as every time I've done it I've got close to 21 hours - just missing out the last time I did it".
He described how, at one point, there are eight locks close together on this non-stop course, which means the canoeists have to run about a mile-and-a-half in one go.
Two hundred kayaks and canoes will set out from Devizes, with the quickest boats hoping to finish early on Easter Sunday.