England's Tom Hamer set a new British record to win silver and Wales' Jack Thomas took bronze in the Commonwealth Games Para-sport S14 200m freestyle.
The event, won by Australia's Daniel Fox, was the first at the Commonwealth Games for swimmers with learning disabilities.
Fox set a new world best of one minute 57.16 seconds in qualifying.
But he failed to improve in the final, winning in 1:57.68, ahead of Hamer (2:00.27) and Thomas (2:01.27).
"I came in here ranked fourth so I didn't really expect a medal. I am really shocked," Thomas, 19, told BBC Sport.
Hamer, 15, whose time beat the 2:01.27 set by Dan Pepper in 2011, was thrilled with his silver medal and British record.
"I'm well chuffed. I'm so happy with it," said the Burnley swimmer.
Both Hamer and Thomas will be competing for Great Britain at the IPC Swimming European Championships, which take place in the Netherlands from 4-10 August.