Jack Burnell became the first British athlete to qualify directly for the 2016 Rio Olympics by finishing fifth in the World Championship 10km marathon swimming event in Kazan, Russia.
While 103 athletes have so far won places for Great Britain at the Games, or hit qualifying standards, Burnell is the first to win a named place.
The 22-year-old's place is expected to be ratified early next year.
"I came for a medal, but the main thing was the Olympic place," said Burnell.
The Scunthorpe-born swimmer finished in one hour 50 minutes and 5.8 seconds, just 5.1 seconds behind bronze medallist Spyridon Gianniotis of Greece.
USA's Jordan Wilimovsky took the title with Dutchman Ferry Weertman second.
|Jack Burnell at a glance|
|Born in Scunthorpe in 1993||15th in 10km world championships in 2013|
|Silver in 800m and 1500m in 2013 national championships||Runs a custom sportswear company|
Payne then finished fourth at London 2012, with Daniel Fogg fifth in the men's event.
"To be honest, something just didn't feel right today, but I know I can challenge for a medal in Rio," Burnell, who is the current open water World Cup leader, told BBC Sport.
"Hopefully this is just part of the journey to that."
His official Team GB selection is expected to be ratified by the British Olympic Association in early 2016 at the same time as the pool-based swimmers are selected.
Burnell's team-mate Fogg was in contention for a medal at the halfway stage, but his challenge faded after being involved in a physical battle around a buoy in the final 2kms, which saw him swallow water and lose crucial time.
With no further Rio Olympic qualification opportunities for British male open water swimmers. Fogg admits he may have no future in the event.
"There's no point carrying on with no more places up for grabs," he told BBC Sport after finishing 14th.
"I need to go home, have a rest and a real think about whether I want to come back and try to qualify for the Olympics in the 1500m event now."
On Tuesday two-time world champion Payne will aim to secure herself a place at the Rio Games.
Like the men, she and team-mate Danielle Huskisson need top-10 finishes to attain named spots for next year's Olympics.
Following publication of this story, it emerged modern pentathlete Samantha Murray had already obtained a named place by finishing fifth at the World Championships - although this was not realised by the sport's administrators at the time.