Strange, the one I did wasn't Warm but not cold by any means. I was expecting it to be colder. Maybe it was from all the people peeing in it? lol
There weren't many people doing ours, I think only 2 other groups of 5 or 6 people and the cave was pretty big so we didnt see them most of the time. I know the water could not have been to cold or the wife would have been complaining more.

I was probably warmer due to swimming for 2 of us since she just held onto the back of my life jacket and I towed her along.