Where I lived as a child and young adult, there were plenty of sand dunes (and marran grass ) within a short biking distance. A group of us used to take bats and balls and packed lunches in Oxo tins (remember boxed individual square fruit pies?)
They were real Famous Five outings, as one friend had a dog which rode in the front basket while being fed pie.
Anyway, on this particular day it was foggy. We hoped it would clear as we rode towards Southport but we had to stop in Formby. Trapsing through the sand with bikes is difficult but we found a hollow and got a game of catch started. One throw sailed over my head and I stumbled through the sharp grasses to find it. Lo and behold, my eyes were assaulted by two 'old' men fondling each other, shorts round their ankles. I had never seen anything like it (we were about 13/14/15) and wondered what they were holding. The others came looking for me, then a policeman appeared behind us as we lay on our tummies, gazing at the spectacle before us.
All did not end well for the two men but I was not keen to tell mum what I'd seen. Maureen, my friend, said not to tell anyone...and I didn't.
The area was well known for nudity, in varying degrees.