Amphitrite are in the family Terebellidae, and live in soft sediment on the ocean floor. They are selective deposit feeders. Special head stuctures extend over the ocean substrate, and move back and forth. Deposit material sticks onto mucous found on these structures, and is conveyed back to the mouth where it is eaten. The worm does not have to leave it's burrow to feed.
Earthworms crawl through the soil, eating sediments or dirt directly.
The pharynx acts like a pump, drawing material into the mouth. We are not aware of any speculation as to why the Terebellid worms have evolved the selective deposit method of obtaining food. It is possible that on the ocean floor, organic debris is located primarily on the surface, so these worms concentrate their food gathering activity only on the top layer of the substrate. Teredo navalis is actually a mollusc specialized for boring into wood. If the ship's hull was metal, it definitely wasn't T. navalis .