Question: I do a lot of swimming in cold mountain water. Exactly how warm does a wetsuit keep you?
Answer: It all depends on the thickness and coverage of the suit.
A 5mm full suit is going to keep you a lot warmer than a 2mm “shorty” springsuit.
People who scuba dive in the arctic use wetsuits to themselves warm so I am sure the right wetsuit can handle cold mountain water.
When you first get in the water you will still feel the cold water, but as the suit allows some water to seep in your heat warms it and you end up feeling much warmer.
The retained body heat and heated layer of water does wonders for keeping you warm.