Rower Sanita Puspure missed out on a place in the single sculls semi-finals by just .65 of a second in Rio.
The 34-year-old finished in fourth place, with only the top three qualifying, in what was regarded as the toughest heat.
The Cork-based woman looked completely out of contention after the halfway mark, trailing the third-place Belarusian rower by a length and a half.
With just 500m to go she seemed to be labouring but surged late on, almost closing a significant gap to agonisingly miss out on qualification by .65 of a second.
The time of 7:28.68 would have been good enough in any of the other three heats.
She can still row in the C & D final but that will prove little consolation. RTÉ analyst and double Olympian Neville Maxwell said it was "four years down the drain".
Australia, China and Belarus took the top three places.
Puspure misses out on semi-final spot - 'She just ran out of water' https://t.co/cBPRMVLCO1— RTÉ Sport (@RTEsport) August 9, 2016