Olowalu, Maui, 10 feet, 24mm

Makapu'u, Oahu, 15 feet, 26mm

Makua, Oahu, 15 feet

Locally common from surf-swept beaches to 30 feet.  Flaring aperture, color variable.  Attains 1.5 inch.  Uses foot to sail in the surge.  Hawaii & Japan.