Geoducks are bivalves, which means their bodies are compressed between a shell that consists of two hinged parts. They have a foot, which helps them dig into the sediment and anchor to the ground. To eat, the mollusk sucks in seawater, filters it for plankton and nutrients, and squirts out the excess through its siphon. This appendage has two openings at the end — one for taking in oxygen and phytoplankton, and one for releasing excess water.