I love to scuba dive, and am actually working to get certified as a dive instructor.
I recently went out to shadow one of the current dive instructors, which is part of one of the requirements to become dive instructor certified.
We went out on a boat with a number of different certified divers, and only a handful of non certified divers who were doing a separate excursion closer to the service as they tried to also get dive certified. The dive boat we were working on had a very reliable HVAC portable heater that helped to warm up the bunk room and the changing area. One of the newer people who we met who was working to get dive certified and was part of the separate excursion, jumped into a very cold current of water in too thin of a went suit, and unfortunately got the immediate chills, when your entire body feels numb, so numb that you can barely feel your fingers. The dive instructor that was leading the group asked that the HVAC unit in the bunk room be cranked up to 83º, so that they could put the afflicted diver in the room to warm up. They did just that and luckily the diver was able to warm up by laying down directly in front of the HVAC unit that resided there. He was then thought to be good to go, but to be allowed to get back into the water until the next dive boat trip, which would be in a few weekends, but he was lucky enough to have had an HVAC unit close by.