Mollusks that live on land move quite slowly on a foot, while mollusks that live in the water send water out of their bodies to propel themselves. Most mollusks have a softer organ protected by a hard shell or are simply immobile.
The most commonly known land mollusk is the snail, although slugs also fit into the same classification. Both of these mollusks emit a lubricant that allows their foot to propel them more easily along the ground, although the progress is still very slow.
Squids, scallops and octopi all use jet propulsion to get around the ocean. The squid has a cavity inside its body that it uses to eject water and push it in a desired direction, as does the octopus. The scallop shuts its shell firmly, ejecting water and sending it across the water.
Oysters and clams are examples of mollusks that do not move. They find a rock or some other surface and attach themselves to it. Then, they filter particles of food from the water that moves through them.
The mussel is an example of a mollusk that lives in water but uses its foot to get around. A mussel lives in a small section of a stream bed or lake, and then slides its foot into gravel or sand and moves along the bottom. This helps it escape low water levels and find better living environments.