Keri-Anne Payne and Cassie Patten claimed silver and bronze in the 10km open water swimming to get Britain off to a flying start on Day 12 of the Games.
Payne and Patten led for much of the race before being overhauled by Russian world champion Larisa Ilchenko in the closing stages, who crossed the finishing line in a time of one hour 59 minutes 27.7 seconds.
Payne came home in 1:59.29.2 with Patten finishing in 1:59.31.0.
The early success added to Britain's burgeoning medal tally which now stands at 35 with 16 golds, 10 silvers and nine bronzes.
Payne and Patten's medals added to those gained in the pool earlier in the Games - Rebecca Adlington landing two golds and Joanne Jackson weighing in with a bronze.
David Davies could add another medal tomorrow when he competes in the men's 10km race.
But despite adding two medals to Britain's record tally, the failure to win gold was a cruel blow to both British girls.
Multiple world champion Ilchenko set the pace in the opening stages but was soon overtaken by both Payne and Patten as the British pair dictated proceedings.
Ilchenko, who defeated Payne at the death during the world championships in Melbourne last year, adopted her usual tactic of sitting on the feet of the leading pair, allowing the British duo to pull her through the water with the minimum of effort.
But with 1 hour 32 minutes gone, Patten and Payne made a move to try to string out the race, upping the tempo in an effort to reduce the medal contenders.
Ilchenko, not surprisingly, remained in touch, as did Brazilian Poliana Okimoto, Andreina del Valle Pinto Perez of Venezuela as the attempt failed and the bulk of the group came back together.
As the swimmers went round the final buoy the speed increased again as the pack started jockeying for position.
Patten and Payne, though, remained at the front, unable to shake off the attentions of the other contenders.
With 250 metres to go, the medal contenders were whittled down to just four, with Germany's Angela Maurer joining Payne, Patten and Ilchenko at the front.
Maurer, though, was unable to match Ilchenko's burst of pace as the Russian pulled alongside the British pair. Payne fought back, matching her stroke for stroke until, somewhat inevitably, Ilchenko inched ahead to touch ahead of Payne with Patten taking bronze.