Swim cap watertightness varies with the model. A mesh swim cap is not waterproof at all, allowing water to pass through. A silicone mesh swim cap is made up of waterproof panels; while water can still pass through its seams it offers greater protection from splashes. Silicone caps provide greater watertightness thanks to their composition. ATTENTION: NO SWIM CAP IS 100% WATERTIGHT; WATER SEEPS UNDER THE CAP PARTICULARLY AROUND THE EARS.