I live where the water barely gets warm enough to swim in during the summer, so kayaking is often a dry suit activity. When I was taking a class I had quite a time staying cool. Some people flip on purpose, or you just shove as much of an arm into the water as you can and wait. A dry suit makes 50°F water feel like a crisp morning with still air, instead of torture.

Water inside reduces that insulation. I wore my synthetic base layers underneath just in case.