It’s called exposure protection because while scuba diving you’re not only exposed to water’s cooling ability but also to things that can scrape, cut or sting.
Wetsuits get their name because you still get wet while wearing one. Your body quickly heats the thin layer of water that gets in and you’re insulated from the cooler surrounding water by the wetsuit material. You choose your wetsuit style and thickness based on the water temperature where you’ll dive.
Kirk Scuba Gear offer a variety of wetsuits from dive skins to 7mm for the diver.