Canon Slade School pupil Niamh Robinson finished seventh in the semi-final of the 50m breaststroke in representing the Isle of Man with a time of 33.38.
The time was just one tenth of a second down on her personal best set in the heats earlier in the day.
The 14-year-old will be in action again tomorrow in the 50m fly and 200m breastroke.
Mum Suzanne said: “Niamh has swam her heart out. A great PB in the heats saw her qualify for the semi-finals and we are so proud of her.
“It was so much more than we had ever expected.”