Competitors will face their worst fears in this weekend's Avon Descent with the lowest water level on record.
The 40th anniversary of the white-water classic was expected to be a celebration but instead competitors are bracing for a two-day slog from Northam to Bayswater.
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Race director Jim Smith has forecast that injuries and damage to craft are to be expected.
"There will be a race but no records, it certainly won't be a walk in the park," Smith said.
"We looked at the course during a low flyover and all we could see was rocks, rocks and more rocks."
Paddlers will race the full 124km with some minor exceptions - 50km has been trimmed off the most treacherous stretches for all but the top power dinghies.
South African world champion Hank McGregor, the winner of the past two Avon Descents, said he vowed never to race in low water again after his 2010 experience.
"I came back last year and had a great race so I talked my partner Grant van der Walt into coming here with me this year and guess what, the water is even lower than in 2010," he said.
"It looks like it is going to be one of the toughest white-water events in the world this year."
One of the biggest problems is that the top paddlers will be racing in double kayaks, which are less manoeuvrable than single craft, increasing the risk of boat damage, he said.
"Obviously we will be sitting deeper in the water and hitting a lot more rocks which is going to make it a lot harder," McGregor said.
He said it would be a huge shock for his partner, the world under- age marathon kayak champion, who had never been to Australia.
"The hardest thing about this race is going to be pacing yourself - we have been preparing for a four or five-hour race each day and suddenly you come here and find out the winning time is going to be a lot longer," McGregor said.
"You have to remain focused because you don't want to make mistakes and damage your craft."
Double kayak record holder Darryl Long, the winner of 13 titles in 30 appearances, said the Australians wouldn't have any advantages over the South Africans, who have dominated the race for the past decade.
"We don't practice in low water so we don't know the course better than anyone else," he said.
"It is going to be tough in a double; the single would have been much easier. So everyone will have to look after their boats a lot better to make sure they make it to the finish."
Another winner, Daryl Bartho, who will be teaming up with South African Grant Woollaston, said the key to the race would be to survive the first day's racing.
"It is going to be a matter of nursing the boat through the valley before the real racing starts on the second day," he said. "A broken boat or broken seat could cost you a lot of time. You have to conserve all the way and tackle it as an ultra endurance event."
The crews who make the best decisions at the right time would be the ones who survive the first 40km, he said.
"In 2010 we would have got in and out of the boat fifty times and this year, being in a double which is even heavier and less manoeuvrable, there is going to be a lot more dragging," Bartho said.
Power boat champion Ian Williamson, who with son Todd has won four times in the last seven years said the race could possibly be tougher for the power crews than the paddlers.