A team of four men attempting to row non-stop around the British coastline expect to reach Land's End on Monday.
The team is made up of three Grenadier Guardsmen and a businessman
Lt William de Laszlo, 25, London; Sgt James Bastin, 35, of Gloucs; Lt Ben Jesty, 24, London; and Will Turnage, 26, of Hants, began the trip on 7 June.
Called the GB Row Challenge, the rowers, of whom three are Windsor Grenadier Guards, plan to travel 2,000 miles - about 50 miles every day.
They are hoping to enter the Guiness Book of WOrkd Records if they succeed.
Until Sunday the men, who aim to raise £1m for the Outward Bound Trust and the Bud Flanagan Leukaemia Fund at the Royal Marsden Hospital, Surrey, were averaging 80 miles a day until they hit bad weather off the south west coast of Cornwall.
Team leader Lt de Laszlo said: "We have to get past Land's End before Tuesday to take advantage of the 30-40 mile and hour southerlies which are due on Wednesday.
"If we get this right, those winds will help to blow us along in the Irish Sea.
"We have been lucky with the weather so far but we knew it was too good to last."