More than 100 children took part in the first aquathlon at the Wantage Leisure Centre in Portway.
Children from the ages of eight to 16 took part in the competition, which involved running around the centre and swimming in the pool.
Ben Hutchings is pictured, nearing the finishing line.
The winners in 10 categories from the regional event will progress to finals later this year.
The British Triathlon Association event aims to encourage more children to take part in sport.
Event organiser Catherine Fourcampre-Maye said: "For two hours the children took part in what was a gruelling challenge but they all did very well."
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