Actually Whelks are quite bloodthirsty creatures:

Lightning Whelks live in sandy shallows from below the tide mark to deeper waters. These predatory carnivores bury themselves just under the surface of the sand where tender mollusks they like to eat are easy to find. Clams, scallops and oysters are favorites. The whelk attacks its prey in two ways. Either it grabs the bivalve with its big foot and pounds it apart on its own strong shell, or it inserts the outer lip of its own shell between the valves to force them apart. (From this informative page.)

Move over, Jaws...