Wetsuits are designed to let in water but not to let it out. This means that the water that is accumulated in your wetsuit will heat up to match your body temperature and act as a thin layer of protection to keep you warm.

Can a wetsuit keep you warm in the winter?

The myth is this: Wetsuits keep you warm by trapping a thin layer of water between your skin and the suit. This is incorrect. A wetsuit that is bone-dry on the inside will actually be warmer than one that's wet.

How much warmer will a wetsuit keep you?

Measured in millimeters, the thicker the wetsuit is, the colder temperatures it allows you to handle. A 7mm suit can withstand temperatures around 38 degrees. Have a suit that is less than 2mm, and you can only go into water around 70 degrees or better.