I was reading earlier about somebody that was new to wild swimming and their first time in, they did forty five minutes at the beach... so assume the sea?
I live in Wales, and of course the nurses, carers that come out to you tend to chat to their patients.
One of my Mother's carers was a wild swimmer and she said that you were only allowed to do fifteen minutes a day?
Maybe different rules for different for different waters? E.g. Rivers, Canals, The Sea, etc.
I wouldn't have a clue, but I'm really intrigued now, and would love to delve deeper.
Ironically, I babysat her kids when I was I teen