More than 25% of body heat is lost through the head and extremities of the body. The Sharkskin Chillproof sleeveless top with hood is designed to be worn underneath your wetsuit to provide the best warmth and insulation for your torso for colder dives. The hood protects against chafing from mask straps, keeps your head and ears toasty warm and is flexible enough to slide down around your neck in-between dives while on the boat or back on land while remaining comfortable. The Chillproof material allows for better hearing and less chance of ear squeeze than traditional neoprene hoods.