Windsurf clothes are more appropriately called wetsuits, or in extreme cases, dry suits. The difference is an important one. Wetsuits operate by trapping a thin layer of water against your skin. This water is then heated by your body, and it acts as a thermal barrier to ocean water. Why is that important? Even warm ocean water is only 85 degrees or so. That is still almost 14 degrees below your body temperature.
If you aren’t wearing proper windsurf clothes: a wetsuit, prolonged exposure to ocean water becomes an uncomfortable experience. If you are in a warm climate it is a simple thing to climb out of the water to warm up, but it is much easier to wear a wetsuit and stay warm while in the water.
A dry suit is a type of windsurf clothing that suited for more extreme temperature differences, such as the 40-50 degree waters found up closer to the poles. A dry suit prevents water from coming into contact with your skin at all, and acts as a thicker thermal barrier than the one a wetsuit creates. This allows you to safely spend time in water that would ordinarily cause hypothermia.