This is a picture of a small stream where you might find the shinyrayed pocketbook freshwater mussel living in sand or gravel.

This is a picture of a river where you might find the rabbitsfoot freshwater mussel living in sand, gravel, or cobble.

This is a lake where you might find a paper pondshell freshwater mussel living in mud or sand.

This is what a group of freshwater mussels (or freshwater mussel bed) look like at the bottom of a stream. They look like rocks in the sand, don't they?