Hot Water Suit, a type of diving suit. Diving Unlimited Internation. "The first production hot water suit was built by DUI in 1968"
Never heard of a hot water suit so I looked it up. You can dive in cold water and be very comfortable. Who knew? Being a tiny bit claustrophobic, I would not think of diving in a suit, if at all, even scuba.
So my mom and dad were master scuba divers....they used to say that they each had 'hot water suits' which the dive instructor called 'peeing into your suit' to warm it up.