Children in Wales have been told they will be able to swim and use leisure centre activities free for two hours at weekends all year round.
But the changes to the scheme will mean fewer free swimming hours during the summer holidays.
The new scheme, aimed at those aged 16 and under, will place more emphasis on structured sessions.
Sport Wales said it would help more children "get hooked on sport".
Heritage Minister Alun Ffred Jones will unveil details of the altered scheme later during a visit to Newbridge Leisure Centre, Caerphilly county.
Speaking before the launch, Mr Jones said that since free swimming for children in the summer holidays had been introduced in Wales in 2004 it had been "hugely popular".
The new agreement with local authorities would help deliver the assembly government's aim of every child learning to swim by the age of 11, he said.
"Our research shows that structured sessions are popular and help more children learn how to swim," Mr Jones added.
"As well as ensuring every child in Wales has the opportunity to learn this important skill, making these sessions available at weekends will make it easier for young people to get all the exercise they need.
"Children and young people will also have the opportunity to take part in other free activities at their leisure centre.
"I really hope this encourages them to try new sports and activities which they will carry on into adult life."
'Less holiday sessions'
To deliver the new scheme at no extra cost the assembly government will cut the amount of free swimming it funds during school holidays.
The assembly government said the new scheme would provide local authorities with more flexibility to provide consistent, regular free sessions.
A spokesman that while there would be fewer sessions during the holidays the total number of free sessions was expected to rise.
Some local authorities in Wales have already started offering the new sessions and all are expected to be up and running by September.
Prof Laura McAllister, chair of Sport Wales, said free swimming was helping young people across Wales to undertake regular exercise, and also to learn to swim or improve water safety skills.
"By making Free Swim more accessible, we are one step closer to encouraging more children across Wales to get hooked on sport for life."