Cressi Lontra Hoods have 5mm of warmth teamed up with a smooth neoprene that seals at the neck and around the face keeping the water at bay. They also have a special offset airfree valve on the top of the hood to automatically eliminate any air that may get trapped inside the hood which is perfect for scuba divers. The offset of the two layered valve means that air can escape but water can’t get in.