Really, 100C? Your proteins start to disassociate at around 45, 46C. That means you start making soup out of yourself at half the temperature you are claiming. Now, I like a HOT shower, so my water heater is set to right around 49C, and the water that gets to the shower head is right around 43C. And that can be really uncomfortable enough. I dont think I want to boil myself alive, though.
You are not soaked in water in a sauna. Itīs the mix between heat and humidity that determines how uncomfortable it gets. 70C with lots of steam is worse than 100C and low humidity,