It just occurred to me it is a lot like here in St Louis Missouri. Even in the hottest part of the summer people don't go IN the rivers (Mississippi and Missouri) so much but tons of people go TO the river. Seems to be more of a culture thing than any kind of problem.
I actually did not pay to use the facilities there, was just letting everyone know it is an option that is available. There were several days in the 70s but people didn't even seem to use the pool for more than cooling off and back to sun bathing. Some people would mess around in the lake to about knee level on the weekends but it seems not to be the culture there. Maybe without a sandy beach the water just doesn't call people to swim. I asked the question while I was there and no one had an answer, they just didn't feel like going in, and neither did I.