Shane Ryan has qualified for the European Championship 50m backstroke final after taking second in his semi-final on Friday evening.
However, Darragh Greene narrowly missed out on a place in the 100m breaststroke final after a swim-off.
Greene, from Longford, qualified for the semi-finals and then went to a swim-off with Russian Kirill Prigoda after they both finished in 59.92 - a new Irish record - which was good enough for eighth overall.
When the two got back in the pool, Prigoda finished over a second clear in 59.39 to Greene's 1:00.44.
Big things have been expected of Ryan since he declared for Ireland before Rio 2016 and he delivered in the opening session of the European Championships in Glasgow.
The man from Pennsylvania set a new Irish record of 24.32 seconds and followed that up with a time of 24.57 in the semi, which was good enough for second in the race and fourth overall.
Ryan, whose father hails from Laois, won gold in this event at last year's World University Games and is 2018 Irish 100m backstroke and 100m freestyle champion.
Ryan's 24.32 was the fastest time in the heats and, to put it in context, is only 0.28 off Briton Liam Tancock's nine-year-old world record and the fastest time swam in Europe this year.
Conor Ferguson missed out on joining his compatriot by an agonising 0.03 seconds despite breaking the Irish junior record for the second time today.
The Antrim man smashed it initially when clocking 25.08 in his heat as he qualified 11th for the semi-finals. He then swam in 24.99 to take fifth but it was not quite enough to send him into the final. He was ninth overall.
Earlier today, Ireland’s 4x100m Freestyle Relay of Ryan, David Thompson, Jordan Sloan and Robbie Powell swam an Irish Senior Record of 3:17.55.
The quartet took almost two seconds off the 2017 record (3:19.39) to finish fourth in their heat and twelfth overall.