The compression of their shell's valves force water through jets, and that force helps direct the shell in the direction of the shell's opening.
Les Kaufman, a Boston University professor of Marine Biology, confirmed to BuzzFeed News that the subject of the viral video is indeed a scallop — and "that mollusks can move."
"I think the problem with folks not knowing that mollusks can move is that they do not realize that mollusks are animals in the first place," Kaufman said. "Yeah, it’s a scallop. Moving normally, as they do, jetting water by clapping their shells together."