I sat in a lukewarm hot tub last month, because I didn't work the controls properly (no markings, turned it one way, it was cold, turned it the other, it was lukewarm. As I was in the tropics and it was early in the morning, I figured the hot water wasn't on yet, so sat in my 'hot' tub in lukewarm water - not ideal, but not terribly bad given the fabulous view from the balcony the hot tub was on. It was only a couple of hours later when my companion used the shower, that my error was pointed out - had I left the 'cold' side on for a minute, it would eventually become hot - the lukewarm was the cold side!)