Mollusk

Example:

Imagine trying to move a heavy suitcase across a sandy beach. Just as you have to use your muscles and a careful strategy to drag the suitcase smoothly, a mollusk uses its muscular foot to move across surfaces. The suitcase represents the shell that some mollusks carry, providing protection but also adding weight, while the sandy beach illustrates the various environments mollusks navigate using their soft bodies and muscular foot, much like you maneuvering across the sand.