How are molluscs adapted to their habitat?

Molluscs are very defenseless in the aquatic environment, so their body is protected by a hard shell, only some terrestrial species are not. Those who live in water feed by filtering water through themselves. A beneficial aspect for humans is clean water. The mollusks move with the help of their legs, although the speed of movement is insignificant. When sand gets into the cavity of the mollusk itself, substances are released that envelop it and form a pearl. In this form, it will not damage the soft tissues of the body.