We all know that wetsuits keep the water out and heat in, but there is much more to these essential suits than meets the eye. Wetsuits are made with neoprene rubber, a closed-cell foam that traps millions of tiny gas bubbles within its structure. Unlike open-cell foam (i.e. a sponge), water won't saturate neoprene, but the gas bubbles tend to give the material a lot of inherent buoyancy. When you climb into a wetsuit your 98.6-degree body temperature warms the gas bubbles in the neoprene, which act as insulation.