Great British duo Kate Haywood and Siobhan-Marie O'Connor have bowed out of the women's 100m breaststroke during the heats.
The former finished eight in her heat with a time of 1:09.22, while her 16-year-old compatriot finished in 1:08.32 in the final heat.
Lithuanian youngster Ruta Meilutyte pulled off a shock by recording the fastest time of the heats, completing the race in 1:05.56.
United States' Rebecca Soni and Breeja Larson also progress to the next phase with respective times of 1:05.75 and 1:06.58.
The women's backstroke semi-finals take place this evening at 7.50pm.
