I would say that the reaction of the staff could be an indication that this isn't the Norm in that swimming baths and this man knows this.
That's all that matters, really.
It isn't just about Gateway crimes, there are a load of disorders, in which the individual likes to get away with behaviour that is outside the Norm, as public as possible.
The intent isn't always sexual, but this builds up.
Staff members are usually aware of who to watch.
My DD runs a residential unit that often involves lots of meetings with not only the persons SW/CPN/Probation officer/Police, but public building managers, to endure her Service User's code of conduct is clear and the consequences of breaking that.
There is difference in behaviour, that is why past serial sex pests, abusers etc got away with what they did, it could be explained and passed off.
I've been in many private Saunas etc and you can tell the difference between someone not thinking anything of shaving, as opposed to someone with their legs up, flashing, enjoying the discomfort/shock of others (for example).