Water temperature

I don't get in here often so maybe this has already been discussed, but what do you all think is an ideal water temperature for swimming? I've always liked 80 degrees. The place I swim at most often (Lifetime Fitness in New Hope, Minnesota) hovered there for most of the winter. Sometimes more, but it usually came back down. Due to a work schedule change I didn't go for a week. I got back in on Tuesday and the temp was 86. I actually cut my workout short and switched to mostly kicking. I asked them to lower the temp and later sent an email. I got back in on Friday and it was still 86. I talked to the front desk and explained. I realize, I'm only one person, but I can't imagine anybody else wanting to actually swim laps, wanting the water to be this warm. Not to mention it being cost effective for operations. The guy said it was up because people complained it was too cold. These are probably older people and/or the people doing those water aerobics. I tell them, man, just move around more and you'll warm up. Or sit in the jacuzzi. More questions: How do I tell if I'm getting overheated w/o actually passing out? Has this happened to anybody else? I recently started wearing a silicone cap, which adds to the problem of releasing heat. I did my intended workout, slower than usual and was pretty wiped out for the rest of the day. Do swimmers sweat in the water? I always thought so (it certainly feels like I am, but hard to tell when you're already wet). But some people say no. Is comparing a runner running outside in 86 degree weather and not being able to sweat a reasonable comparison?