Bangor club swimmer Conor Ferguson has finished in 21st place following the 200m backstroke heats at the World Championships in Budapest.
Ferguson, who recently won a silver medal for Ireland in the 50m backstroke at the European Junior Championships, had a time of 1:59.09 on Thursday.
The 17-year-old needed to be in the top 16 to qualify for the semi-finals.
His personal best for the 200m back is 1:58.80 which was set at the Irish Open Championships in April.
Ferguson's time in Hungary, which was 0.69 seconds outside a qualification place, was the second quickest of his career.
The Northern Irishman now turns his focus to the World Junior Championships in Indianapolis which take place from 23-28 August.
Mayo swimmer Nicholas Quinn produced a season's best in the 200m breaststroke heats to finish 20th.
Quinn clocked 2:12.15 which was 1.15 seconds off qualification.