It was a difficult start to the Olympics for rowers Phillip Doyle and Hannah Scott after they both failed to qualify from their heats.
Team Ireland's Doyle and partner Ronan Byrne could only finish fourth in the men's double sculls heats.
The pair can save their Games when they race in the repechage event on Saturday at 1:40am UK time.
Representing Team GB in the women's quad sculls, Scott and partners finished third in their heat.
The Coleraine native and her team were up against Germany and the Netherlands all the way to the finish but third place means they will also be forced to go through the repechage on Sunday at 2:50am UK time.
Elsewhere, Ireland's reigning World Champion Sanita Puspure easily won her women's single sculls heat and moves on to the quarter finals.
Belfast archer Patrick Huston finished 25th in qualifying in the men's individual competition and will now face 40th seed Brazil's Marcus D'Almeida in the first knockout round.
Huston was the top qualifier of the British trio with James Woodgate in 38th and Tom Hall 48th.
Their standings leave GB as 10th in the qualifiers for the team competition.
In swimming, Ireland's Shane Ryan has pulled out of the 100m backstroke due to shoulder pain specific to the stroke movement.
Instead he will concentrate on the 100m butterfly and the 4x200m freestyle relay, where he does not struggle.
