https://wiki.openstreetmap.org/wiki/Talk:Swimming_and_bathing#Water_were_bathing/swimming_is_forbidden

See also confusion “How is a leisure=swimming_area different than any place that has water? There is always a potential for swimming.” (https://wiki.openstreetmap.org/wiki/Talk:Tag:leisure%3Dswimming_area#Ambiguous_/_redundant_Tag) demonstrating the need for clarification.