Collecting Other Shellfish
Moon Snails are commonly eaten as Scungilli. They are sometimes very common offshore; more than that I can't say.
Large Whelks are sometimes eaten as Conch, but these are most often collected in bay waters.
Clams live beneath the surface of the sand and would be difficult for a diver to collect.
Oysters are also found in shallow bay waters. Oyster diving in the Chesapeake Bay is a wintertime way to get in the water.