The activity will run up until the two-week blackout period ahead of the Olympic Games, which prevents non-sponsors using Olympic athletes in advertising to protect official sponsors, which include British Gas competitor EDF Energy.
The ad uses Psyop animation to create realistic, speaking depictions of the sportswomen.
The campaign offers Brits a chance to show their support for the British Swimming teams. In return they will be given a "free swim" and a chance to try an aqua aerobics or aqua tots class.
The 'Free Swims for Britain' offer can be redeemed in more than 700 leisure centres, health clubs and hotels across the country
Will Orr, marketing director at British Gas, said: "British Gas has supported British Swimming for the last three years and we look forward to continuing this support in the years to come.
"We’re really excited that 'Free Swims for Britain' will help everyone to enjoy spending time in the water during what promises to be an unforgettable summer."
The television spot will be supported by press and digital activity.
The free swims promotion will run until 30 August 2012 and can be booked for free via British Gas's swimming microsite.
The energy company first promoted its 'Free Swim' initiative on TV back in the summer of 2009 and ran the same campaign in cinemas throughout March and April in 2010.
Follow Matthew Chapman at @mattchapmanUK