Andrew Bree clocked 2:10.16 at last year's Beijing Olympics
Andrew Bree bowed out of his specialist 200 metre breaststroke in disappointing fashion at the World Championships in Rome on Thursday morning.
Bree's time of 2:12.90 was almost three seconds outside his personal best (2:10.16) and left him 30th overall.
Bangor woman Clare Dawson set a new Irish 100m freestyle record of 56.32 as she finished 41st overall.
Dawson's time clipped .30secs off Fiona Doyle's existing mark. Karl Burdis also set a new Irish 200m backstroke record.
Burdis clocked 2:04.34 which clipped .39 off Adrian O'Connor's record set back in 1996.
Dubliner Burdis finished 43rd overall.
Doyle joined Dawson in the 100m freestyle heats and her time of 56.96, .34 slower than her personal best, left her 60th overall.
Irish quartet Dawson, Melanie Nocher, Niamh O'Sullivan and Niamh Murphy wiped over nine seconds off the Irish 4 x200 freestyle realy which placed them 15th overall.
Bree reached the Olympic semi-finals last year after smashing his Irish record by nearly three seconds but he was well below that kind of form on Thursday morning.
A time of 2:10.54 would have been good enough to reach Thursday evening's semi-finals.
Bree's preparations were not helped by his body suit bursting before the race but he acknowledged that he had been below par.
Clare Dawson set a new Irish record in the women's 100m freestyle heats
"That wasn't my best performance out there," said Bree.
"It just didn't feel right from the start and felt a little too choppy.
"I'm going to go back now and analyse the race with my coaches and see what I need to do to get back down to my best again."
On Wednesday, Derry swimmer Ryan Harrison went under 50 seconds for the first time to improve the Irish 100m freestyle record to 49.49.
Barry Murphy had earlier improved his own national mark to 49.76 in the heats before Harrison set the new record.
Harrison finished 41st overall while Murphy placed 51st.
Grainne Murphy set a new Irish junior record as she finished 30th in the 200m freestyle while Aishling Cooney didn't progress in the 50m backstroke heats.
Murphy continued her impressive championships as she clocked 2:13.16 in the 200m freestyle while Cooney was timed at 29.46 as she finished 46th in her latest event.
On Tuesday night, Barry Murphy missed out on a place in the 50m breaststroke final by only .14secs as he clocked 27.24 in the semi-finals.
Both Harrison and Barry Murphy used the new generation body suits in the 100m freestyle heats on Wednesday morning.
Barry Murphy became the first Irishman to go under the 50m barrier for 100m in the first leg of the 4x100m heats on Sunday.
Harrison has now set three Irish record at the World Championships after improving his 200m and 400m freestyle marks.