Hard-shells are the most sought after. Soft shell clams cannot close its shell because its neck sas out too far. The largest soft-shell is the geoduck, which may weigh up to three pounds. Sea clams are usually used for canning or in packaged soups.
If you dig your own clams, you must purge them of sand and debris before eating. Allow the clams to stand 20 to 25 minutes in clear sea water. The water should be changed at least three to four times to be sure they are free of residues.