Jo Jackson and Lizzie Simmonds sealed their places in Great Britain's World Championships squad with wins at the National Championships in Sheffield.
Both swimmers failed to qualify at the first trials in Manchester in March but qualified second time round.
Jackson produced her fastest time for two years to win the 200m freestyle in one minute 58.32 seconds.
Simmonds won the 100m backstroke in a time of 59.86 seconds to take the last squad place left for the event.
The return to form of Olympic bronze medallist Jackson was particularly heartening after 18 months of ill-health and severe asthma problems.
"I wanted to go quicker, but to get the qualifying time and book my spot for the worlds, I can't explain how happy I am," she said.
"This time last year I didn't think it would happen so I am so relieved and that is what the smile is for."
Simmonds said the difference between her performance in Manchester and the one in Sheffield was all down to a more positive mental attitude.
"I've just been enjoying it," she said. "I had a dip there and found it quite hard to pull myself out of that.
"With not qualifying in the 100 I got a bit more down and when I didn't qualify in the 200 it was the be all and end all.
"I then reassessed it and looked at my swimming and thought 'this is something I should love doing' and 'I do love doing it?'"
A storming swim by Jemma Lowe in the 100m butterfly saw her pip Fran Halsall by 0.01 seconds to take the second spot alongside Melbourne-based Ellen Gandy, who qualified in March.
Halsall, who had ankle surgery in December, will now concentrate on the sprint freestyle events in China.
Others to make the qualifying time were the 15-year-old Siobhan-Marie O'Connor (200m individual medley), Robbie Renwick and David Carry (both 400m freestyle) and Kris Gilchrist (100m breaststroke).
On Wednesday, Halsall returns in the 100m freestyle, for which she has already qualified, and Renwick and Carry go for one spot in the 200m freestyle.
The World Championships take place in Shanghai from 16-31 July.