World champion Adam Peaty secured his place at the Rio Olympics with gold at the British Swimming Championships in Glasgow.
Peaty won the 100m breaststroke in a world-leading 58.41 seconds, with Ross Murdoch second and James Wilby third.
Peaty told BBC Sport: "There's no better feeling."
World silver medallist James Guy (400m freestyle) and Hannah Miley (400m individual medley) won their events in Rio qualification times.
Welsh swimmer Jazmin Carlin claimed victory in the 200m freestyle final ahead of Eleanor Faulkner and rising star Georgia Coates.
Carlin's time was not quick enough for a guaranteed individual Rio place, but should be enough for the 4x200m freestyle relay team.
Her main events - 400m and 800m - are later in the week.
Peaty set a world record in the event at last year's British championships in London but has plotted a different strategy this season.
"My coach and I were looking at doing it differently and peak for later in the year, so hopefully there are quicker times to come at the Olympics," he said.
Murdoch's time of 59.31 secs is likely to be enough for Rio 2016 selection, but the world championship bronze medallist will return for the 200m competition on Friday.
Guy had to be taken off poolside while he was physically sick following the 400m freestyle final, which he completed in three minutes 43.84 seconds.
"It was a great swim and I'm so happy to qualify for the Games, but it definitely hurt towards the end and I was sick everywhere," Guy told BBC Radio 5 Live.
Scotland's Miley booked a place at her third Olympics after moving clear of long-time English rival Aimee Wilmott in the closing stages to finish in four minutes 33.40 seconds.
She said: "It's always great to come here and was really pushed by Aimee and I owe her a lot for making me get that time."
British swimmers will be nominated for Rio 2016 selection after the trials with the British Olympic Association [BOA] due to ratify the Team GB squad later this month.