Dorothy's snail Boat Shed Beach
Channel: Sean Anderson
Date: 2015-08-05

This is Nerita polita, a common grazing snail across the Indo-Pacific tropics.  These guys feed on microalgae on exposed rock surfaces around mid-tidal elevations, but burrows a few centimeters into sand (presumable as a refuge from predators) when not feeding (see Morton and Burgin,1986).