I’m going to break this down to levels beyond scientific, based on my test data.

I’m proposing a “bust-yer-aise” scale similar to the wind chill factor or the heat index. 80 feels like 88, provided you’re working hard enough.

If 80 degree water in your backyard pool is too cold for you to cool off in, you need to increase the intensity of your run/bike/walk/row/rugby/training. Or mow/landscape harder. Whatever.

And the max temperature for a lap pool should be ~78. If you can’t make yourself sweat buckets in 78 degree water, consult a physician.