A Pembrokeshire beach has become the first in the UK to be declared smoke-free.
The voluntary ban at Little Haven, which also applies to e-cigarettes, came into effect on Wednesday to coincide with National No Smoking Day.
Pembrokeshire council said it took public health very seriously.
But smokers' lobby group Forest accused the council of imposing a policy to "denormalise a legitimate habit".
Thirty-five pupils from Broad Haven Primary School launched the 12-month trial, to highlight children taking up smoking in Wales.
Criticising the scheme, Simon Clark said: "There is no evidence that the sight of a complete stranger smoking encourages children to start smoking.
"The ban on the use of e-cigarettes demonstrates that this is not about health, it's about control."
Huw George, environment cabinet member, said: "We know children are at particular risk from second-hand smoke and that they are more likely to start smoking themselves if they see adults doing it in a family-friendly environment.
"It is vital to denormalise smoking to reduce the rates of young people taking it up and also to reduce their exposure to smoke and e-cigarette vapour in areas where they gather."