Canada's Richard Weinberger won the first swim test event for the 2012 London Olympics on Saturday in a 10-kilometre race in Hyde Park's Serpentine.
The Victoria swimmer finished ahead of Germany's Thomas Lurz, while world champion Spyridon Gianniotis of Greece finished third.
Weinberger, 21, did not earn an Olympic berth at the recent world championships in Shanghai, but will have other chances to qualify.
Italy's Martina Grimaldi won the women's event a month after taking silver in Shanghai.
Grimaldi overtook Eva Fabian of the United States down the final stretch to win in two hours two minutes 49.5 seconds.
Fabian led for nearly the entire race but finished half a second back in second. Brazil's Poliana Okimoto was third and American swimmer Christine Jennings was fourth amid the greenery of London's largest park.