Oysters Oysters have bivalved shells to protect their soft bodies. The shells are attached to each other one one side with a hinge. When oysters are very young, they swim around. Grown-up oysters attach themselves to rocks or other hard objects on the bottom of the ocean. They wait for tiny plants and animals to come to them in the water.
Oysters lay millions of eggs.
The oyster does not live very long because it has lots of enemies. The sand dollar has a hard shell that is purple when it is alive. Sand dollars have tube feet and spiny skins. They are invertebrates having a flat, circular outer shell. The common sand dollar of the notheastern United States is found on sandy bottoms in comparatively shallow water.