Michael Jamieson and Andrew Willis gave Britain real hope of another swimming medal by qualifying first and third for the Olympic 200m breaststroke final.
Scotland's Jamieson set a new British record of two minutes 8.20 seconds in the first semi-final.
Willis set an English record of 2:08.47 as he finished second in his semi.
Willis makes 200m breaststroke final
Jemma Lowe squeezed into the women's final of the 200m butterfly, qualifying eighth fastest to ensure three Britons will contest for medals on Wednesday.
"You have to have a lot of belief just to control yourself in the first 50m and keep calm when you can see people in front of you," said Lowe after qualifying in 2:07.27 for a place in lane eight.
"It was probably a little bit dangerous but it worked perfectly. I feel like I have a little more in the bag but you never know in the final, there's a chance for everybody. I'm just going to give it my best."
Lowe's event was followed by the men's 200m breaststroke semi-final and Jamieson admitted he was "full of confidence" after qualifying fastest for the final, with team-mate Willis third quickest.
"It makes it a lot easier being in front of this crowd with them nudging me forward in the last 50," said Jamieson.
"I'm hoping they can make even more noise on Wednesday night and hopefully myself and Andrew can shave some more time off."
Daniel Gyurta of Hungary won the second semi-final in 2:08.32, and the British pair will face a tough battle if they are to get medals in the final at 19:30 BST on Wednesday.
"I'm going to have to go quicker if I want to improve on that position and make sure I'm in amongst the medals," Jamieson added.
"I'm going to have to find some more time and again the crowd was just amazing and it's making such a difference, and hopefully they can get behind us again tomorrow night."
men's 100m freestyle semi-final
world champion James Magnussen qualified quickest (47.63) for Wednesday's final at 20:20.
He will be joined by his main rivals, double Olympic champion Yannick Agnel, world silver medallist Brent Hayden of Canada and world record holder Cesar Cielo.