The Great Lakes region of the US and Canada is a truly special place when it comes to fresh water. The experiences in this area can't be extrapolated to elsewhere. You can get hypothermia in the middle of a summer heatwave if you spend too much time in the water more than 1km from the shore. Even if you stay at your local beach, most people would find the water uncomfortably cold. In Chicago today, the high temperature is going to be around 18° or 19° C. The surface temperature of the water at the beach is slightly less than 4° C.