Britannica
Sources used in this answer
How do scallops swim by forcing water from their mantle cavities?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
mollusk
Mollusk shell classification chart, c. 1861.
Scallops swim through a form of hydraulic propulsion produced by rapid, repeated clapping movements of their two shells. This process is driven by the adductor muscle, which closes the shell, while an elastic hinge rapidly opens it.
These movements create a powerful water jet. The muscular mantle, a membranous fold beneath the shell, acts as a valve to control the direction of this water flow. Typically, water is ejected downward on each side of the hinge, which lifts the scallop and propels it in the direction of the shell's opening. Additionally, the closed shell's shape functions as an airfoil, which, combined with the downward water ejection, generates lift to assist in swimming.1