World champions Switzerland missed the chance to qualify directly for the Olympics men's pairs semifinals, beaten by two-hundredths of a second by Ireland in a thrillingly tight heat at the Vaire-sur-Marne Nautical Stadium on Sunday.
With three of the five crews going through, the Swiss team of Roman Roeoesli and Andrin Gulich were pipped on the line by Ireland's Ross Corrigan and Nathan Timoney, who came third behind Spain and New Zealand as 0.43 seconds separated the top four.
"When you need to go, you just go so - once you realise what you need to do I think the adrenaline kicks in, and then you just head with it," Timoney told Reuters after their razor-thin margin over the Swiss.
"It was a moment of anxiety waiting for the results, definitely a very tense moment, but thankfully our names are up on the board for the top three," he said.
The grey drizzle of Saturday's competition was replaced by bright sunshine and soaring temperatures as racing began early on Sunday.
Twice Olympic champion Helen Glover and her British teammates came storming back to win the first heat of the women's four in the fastest time of the day, and they will be joined in the semifinals by New Zealand, Netherlands and Romania.
In the men's four, New Zealand set the pace to qualify directly, with Britain, the United States and Australia also going through.
Reigning Olympic lightweight double sculls champions Paul O'Donovan and Fintan McCarthy, of Ireland, cruised into the semifinals, winning the last heat by more than seven seconds to advance with Norway, Switzerland, Spain, Italy and the Czech Republic.
In the women's lightweight event, the New Zealand pairing of Shannon Cox and Jackie Kiddle recorded the fastest time in the heats as they booked their spot in the semis alongside France, Romania, the United States, Britain and Greece.
Sunday's unsuccessful lightweight crews will have another chance in the repechage on Monday.
Tokyo bronze medallist Liu Zhiyu of China grabbed his second chance in the men's double sculls with new partner Sulitan Adilijiang by finishing third in the four-team race, just enough to edge out Italy for a place in Tuesday's semifinals.
The repechage for the single sculls kicked off the day, with Joanie Delgaco of the Philippines setting the pace for the women and Isak Ivan Zvegelj of Slovenia leading the men as they secured spots in the semifinals.