Distance swimmers Adam Faulkner and Graeme Smith have booked their Athens places with medal successes in the Olympic trials in Sheffield. Faulkner, of Nottingham's Nova Centurion, finished ahead of Smith (Stockport Metro) and David Davies (Cardiff) in the 400m freestyle.
Matt Kidd set a British record in the men's 100m freestyle, while the women's 100m butterfly standard went twice.
Ros Brett's new record was beaten by Georgina Lee in the very next heat.
Faulkner, Smith and Davies all three finished inside the required qualifying time of 3mins 50.81secs, the 12th fastest ranked time in the world last year, but only two go through for selection to Team GB.
"It's a great feeling to have qualified," said Faulkner.
"I took a year out from University to concentrate on my swimming and it's paid off. I hope to go to Athens now to see what I can do."
Scotland's Smith, whose main event of the 1,500m freestyle is yet to come in the five-day long event, was also happy to have made the British team after missing out in the same event four years ago.
"If you get it wrong here it's all been a waste of time. The last 12 years would have been for nothing."
Davies, who was disappointed to have made the qualifying time without finishing in the top two places, will be in action later in the week when he also goes in the 1,500m freestyle.
There were other notable performances on the first day's swimming despite only one final being staged.
In the heats of the women's 100m butterfly Loughborough University's Brett became the first British women to go below 60 seconds when she broke the British record of 1min 0.24secs with a time of 59.84secs.
But previous holder Lee, of Birmingham's Camp Hill Edwardians, went even faster in the next heat to reclaim the record in 59.72secs.
Leatherhead's Kidd also set a new British record in the heats of the men's 100m freestyle when he beat his own previous best of 49.72secs to qualify fastest into the semi-finals in 49.65secs.