I swim alot, and have done for years, at many pools, public and private. I've never seen any evidence of male harrassment. Ever.
Lucydo I used to swim a lot, I had a man shout and scream at me when i dared to swim faster than him - he was a slow poke in the medium/fast lane and funnily enough he said fuck all to the man (who was bigger than hin) who had just left our lane. We get a lot of men wuth fragile egis who cant handle a woman swimming faster than him, I've seen other men deliberately try to push women out of the fast lanes even though its the men who arent fast.
Another man was staring at me whilst i swam, then followed me into the near empty changing village by who took the shower right next to me (theres 3 separate group showers with 8 shower heads in each) , then he went into the cubicle next to me (despite like the showers, I'd chosen a cubicle that wasnt the easiest one to walk to, to trst if he was following me) and then he proceeded to push loads of his clothes under my side of the cubicle - I had strong suspicions he was either trying to sneak his phone hidden in the clothes or as a distraction to film me over the top. I legged it sharpish as it was dark and i didn't want to face this guy alone in a dark empty car park.
Then there was a group of about 4 or 5 men who were taking it turns to go under the water to leer at women in the pool then loudly laugh and talk about the women's bodies amongst each other.