US Patent 6854133 Protective headgear for whitewater use

Protective headgear configured for protection of a portion of a wearer's head, including a resilient outer shell, a layered composite liner including a multiplicity of deformable layers, each layer having a different stiffness than adjacent layers, and wherein a layer has a higher stiffness than that of adjacent layers on either side, and a retention system configured to resist upward/rearward rotation of the headgear with respect to the wearer's head to expose the forehead, due to hydrodynamic or aerodynamic forces.