Childrens swimming life jackets Dual-Layer Neoprene Wet neoprene greatly increases in size by roughly 10%, depending on thickness and materials. We use both external and internal neoprene layers to minimize this effect. Dual-layer neoprene keeps the vest fitting as intended and helps to reduce chest expansion in the water. Feather Weight Foam There are two ways to keep a life jacket as light as possible. Reduce water absorption and use the lightest materials we can get our hands on. Our feather weight foam is the best of both worlds, no kidding, feel for yourself.