Voluntary beach smoking ban at Swansea's Caswell Bay starts
A second beach has been declared smoke-free in Wales.
Swansea council selected Caswell Bay for its pilot voluntary smoking ban because it is popular with families.
Little Haven in Pembrokeshire became the UK's first beach to be declared smoke-free in March.
Smokers' group Forest said councils had "no business banning smoking in outdoor public areas". Anti-smoking group Ash Wales said it would reduce children's exposure to seeing people smoking.
Councillor Mark Child, Swansea council cabinet member for wellbeing and healthy city, said: "We are trying to reduce the frequency of smoking around children.
"Cigarette butts are a big element of rubbish on beaches too, so this will add to the clean and healthy environment we all want to have when we visit the beach."
But Forest director Simon Clark said: "The council is treating adults like children.
"The overwhelming majority of smokers know to smoke with consideration for those around them.
"The council should allow them to use their common sense without imposing yet another petty regulation."
Councillor Mary Whitewright, chairman of The Havens Community Council, who walks daily at Little Haven, said she had not seen anyone smoking on the beach since the voluntary ban began, although she admitted it was early into the season.
Ash Wales chief executive Suzanne Cass said: "We know that seeing smoking highly influences young people and it is imperative we do anything we can to stop the renormalisation of smoking."