Johannesburg - Len Jenkins and Hank McGregor finished first and second after leading the pack for most of the way on the first day of the Hansa Fish River Canoe Marathon in the Eastern Cape on Friday.
The pair, who started the race well, struggled later on with both of them falling out of their boats twice.
The race presented challenges for other paddlers as well, according to the organisers, especially for those not used to local conditions.
"It was very frustrating for us because we are not used to using pedals and rudders in Europe," said Czech paddler Jakub Adam.
"We competed against Hank and Len at the world champs in Rome recently and know them to be strong river paddlers.
"We are more used to flat water, but we are working hard on rivers so that we can do well in The Unlimited Ozzie Gladwin next month in KZN."
The course on Saturday will mostly be flat water, and Adam said he and fellow Czech paddler Michael Odvarko hoped to close in on the top 10 by the time they finished the 40km stretch ending in Cradock.
Adam's sister, Anna Ardova, finished in 10th place in the women's section.
She was expected to gain a few positions in the second and final leg.