These bivalves live in the calmer waters of and bays and estuaries. Many of the oyster shells found in the surf of barrier islands may actually be hundreds or thousand of years old. Over the millenia, as these islands have moved closer to shore, old oyster bars in bay side of the islands have been covered with the sand and other material. In time the islands eroded have still further, exposing this material to the wave action of the sea.
The eastern oyster is found primarily in bays and estuaries along the eastern seaboard. A commercially valuable species, it attaches itself to rocks or other hard substrates, sometimes each other. Oysters may grow to 10 inches long and shell shape can vary greatly depending on the substrate that it is attached to. The thick hard shells tend to be grayish. The eastern oyster is plagued by a host of enemies and very few of the millions of eggs produced by a single female oyster will actually grow to maturity. The free swimming veligers affix themselves to almost any hard surface even other oysters and become spat(young oysters).