Hannah Miley came agonisingly close to a second World championship medal but had to settle for fourth in the 800m freestyle final.
Miley, who won 400m individual medley gold on Wednesday, finished in eight minutes 16.09 seconds.
She was edged off the podium by USA's Chloe Sutton. New Zealand's Lauren Boyle took gold ahead of Lotte Friis of Denmark.
"I'm happy because I wasn't too far off my best," Miley, 23, told BBC Sport.
"Obviously I would have loved to have touched for bronze but the 800m for me is just about getting a little more international race experience.
"Repeating the time I did at the Europeans [8.15.66] would have been great but it's all part of the learning process for me."
Despite qualifying with the third quickest time for the 100m backstroke final, Georgia Davies finished fifth, but in doing so set a new personal best and Welsh record of 57.32 seconds which was just 0.14secs from bronze.
"Going in third it gives you the idea that perhaps you could sneak a medal but it's my first time at world short course," said the swimmer.
"It was quite a big deal so perhaps it was unrealistic that I should get a medal but I had the hope.
"I improved from heat to semi to final with the time so I can't be too disappointed."
With the GB men's 4x200m freestyle relay team finishing seventh there were no British medallists on the second day of competition in Istanbul.
However, Lithuania's 15-year-old Ruta Meilutyte, who is based in Plymouth, backed up her surprise London Olympic 100m breastroke gold with her first world title in 50m breastroke.
"I'm really pleased. I didn't expect to do that and I still can't quite believe it," Meilutyte told BBC Sport.
"Training there [in Plymouth] is really good for me and I'm swimming well but I don't think about being a favourite for anything. I just do my thing and have fun."
The teenager will return on Friday for the 100m individual medley final where she'll be joined by Stockport Metro swimmer Sophie Allen.
In the night's other major final South Africa's rising star Chad Le Clos, who defeated Michael Phelps at the London Olympics, again bettered his American rivals - Tom Shields and Ryan Lochte - to claim 100m butterfly gold.