A £140m scheme to offer free swimming pool use to people aged 16 and under or over 60 in England has been launched.
From Wednesday, it will benefit 20 million people in areas where councils accepted government cash to cover the cost of the initiative.
More than £31m has been allocated, with a further £50m being made available to improve facilities.
But about 140 councils turned down funding, saying they could not afford to offer free swimming to children.
For example, council leaders in Mansfield - home of double Olympic champion Rebecca Adlington - said they were offered £49,000 per year.
They claim they would lose out on around £250,000 in annual revenue if they granted the free access.
I hope that by making swimming free for so many in this country we will encourage people to find the time to swim
Actor and cross-channel swimmer
In Wales, the assembly already funds free swimming for under-16s during the school holidays and for over-60s at other times.
Individual local authorities are responsible for their own pricing policies in Scotland and Northern Ireland.
The scheme in England was launched at the Eltham Centre, south east London, with the backing of 400m freestyle world record holder Joanne Jackson, Paralympic gold medallist Heather Frederiksen and Olympic swimmer Mark Foster.
The cash injection, announced last June, is part of a promise to help get two million people more active by the time London hosts the 2012 Olympics and Paralympics.
The government says four out of five - or 288 - councils in England have signed up to provide free swimming for over-60s at more than 1,000 pools.
However, 207 are offering it to young people.
Funding aimed at covering the cost of free pool access, during standard swimming sessions, is guaranteed for at least two years.
Culture, Media and Sport Secretary Andy Burnham said: "This is a landmark moment in our bid to build a healthier and more active nation.
"It is real evidence of our ambition to use the Olympic and Paralympic Games to lift sport in this country."
He said it was evidence of the impact the London games would have.
The first round of grants to modernise facilities - worth £19.2m - have been confirmed for 54 projects across the country.
The biggest awards of more than £1m will go to improved or new facilities in Leicestershire; Calderdale, West Yorkshire; Nottingham; Waveney, north east Suffolk; and the London boroughs of Southwark and Harrow.
A national network of swimming instructors will also be recruited to offer 100,000 free lessons to non-swimmers.
The scheme is being backed by actor and comedian David Walliams, who swam the English Channel for Sport Relief in 2006.
He said: "Swimming has been a real passion of mine since I took it up as a small child.
"I hope that by making swimming free for so many in this country we will encourage people to find the time to swim."
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