A leafy hornmouth shell (Ceratostoma foliatum) is very ornate and has three large “sails” extending outward.  If a leafy hornmouth gets dislodged from a rock and falls down through water, the wing-like processes help to orient the shell so that it lands on the bottom with the opening facing downward.  This helps the snail avoid predation and also quickly get a firm foothold on a new surface.