Better quality polyurethane gear is carefully bonded in many thin layers to prevent water absorption that can result in eventual delamination. Neoprene is the most flexible and durable of the coatings. It's very popular in England and other areas where boating is not just wet, but cold, and boaters are willing to suffer the weight and the cost for guaranteed waterproof gear that lasts. Breathable fabrics allow perspiration and condensation inside the suit to pass outward. Body heat and the higher pressure of humidity drive out the weather vapor.
Some breathable gear is designed to wick water away from the skin.
What to Look For If you are considering non-breathable foul weather gear, look for an inner lining coated with urethane or some other material that allows condensation to collect on the outer shell without drenching you inside, and look for an open bottom or netting that allows the water to drain. Basic fabric weights range from two to seven ounces per square yard. Four ounces is fairly standard for offshore boating. For tropical climates, go lighter. Look closely at the seams and make sure that every stitch is sealed to prevent water penetration.