Adam Peaty and Jazz Carlin both claimed silver medals as British records tumbled on the second day of the World Short Course Championships in Doha.
Carlin was second to Spain's Mireia Belmonte in the 800m freestyle while Peaty set a British record as he was runner-up in the 100m breaststroke.
Peaty joined Siobhan-Marie O'Connor, Fran Halsall and Chris Walker-Hebborn to win 4x50m mixed medley relay silver.
And they set a new British record as they came second to Brazil.
They finished in one minute 37.46 seconds, while 19-year-old Peaty posted a time of 56.35 seconds as he finished runner-up to Brazil's Felipe França Silva.
O'Connor, competing in the 100m individual medley, beat her own British best twice in a day to reach Friday's final as the fastest qualifier in 57.66 secs.
Walker-Hebborn and Peaty joined Adam Barrett and Ben Proud for the men's 4x50m medley but finished fifth with a British record of 1:32.30, having already broken the previous best in the heats. The winning Brazilian team set a new world record of 1:30.51.
Proud set a new personal best time of 21.44 secs in the men's 50m freestyle semi-finals, but missed out on a place in the final.
Georgia Davies finished last in the women's 100m backstroke final, in which Hungarian Katinka Hosszu continued her domination of the event with a new world record time of 55.03 secs.
South Africa's Chad le Clos defended his world 100m butterfly title with another world record-breaking swim of 48.44.
Lithuania's Plymouth-based Olympic champion Ruta Meilutyte beat her closest rival, Jamaica's Alia Atkinson, to women's 50m breaststroke gold.
The five-day championships runs until Sunday, 7 December.
Great Britain team
Men: Adam Barrett, James Guy, Adam Peaty, Ben Proud, Chris Walker-Hebborn.
Women: Jazz Carlin, Georgia Davies, Fran Halsall, Hannah Miley, Siobhan Marie O'Connor, Sophie Taylor.
|Swimming championships explained|
|'Long-course' championships - swum in 50m pools - are traditionally the blue riband events|
|However, 'short course' championships - swum in 25m pools - have been growing in popularity|