Payne missed out on gold in Beijing to Russian Larisa Ilchenko
Britain's Keri-Anne Payne and Dan Fogg qualified for the World Championships by winning the women's and men's 10km races at the Open Water Cup in Israel.
Olympic silver medallist Payne won in one hour 56 minutes 16 seconds, 11 seconds ahead of Cassie Patten.
Fogg touched in 1:50.46, with Tom Allen finishing sixth in 1:50.53.
With the two fastest male and female Britons making July's Open Water worlds in Quebec, Olympic bronze winner Patten and Allen complete the British line-up.
"Payne and Patten completely dominated the women's event from start to finish and showed their class and experience over a fantastic course," said British team leader Mark Perry after the event at the Royal Beach in Eilat.
"Fogg's victory was impressive as he showed all the experience he's gained over the last two years. He swam his own race and on the last lap made his break and made it stick."
British 1,500m champion Daniel Fogg had been expected to lead the British charge at the Red Sea coast race, with Olympic silver medallist David Davies concentrating on the pool this year.
Payne added gold at the World Aquatic Championships in Rome in 2009 to the Olympic silver she claimed in Beijing in 2008 but she has never won a medal in the discipline at the Open Water worlds - a separate biennial event.