The 'Shower Guy' story is a good example of the activities in public shower blocks of tourist parks in any land.
Most consist of a row of shower cubicles, usually with a gap under the dividing wall of each. This dividing wall allows a view of the reflection of the other occupant caused by the over-head lighting and the wet floor, thus creating a mirror effect.
Near the beginning of my 6 years touring by caravan I noticed the man next door was masturbating and I was witness to the entire act. This caused me to take particular notice every day and I can assure you that this practice is very common among the more senior tourists who have menopausal wives. I deliberately chose a cubicle that was bordered by 2 others and I expected that it was probable that at least one cubicle would provide a show. I am near enough to certain that my activities were observed by them also.
The 6 years provided literally many 100s of these performances, and it was not unusual to have the 'evidence' of the previous occupant left on the wall or floor by many of them.