Here's a checklist of the species I have taken off of various beaches around Charleston, SC. These include Folly Beach (southeast barrier island), Isle of Palms (Mt. Pleasant) and Sullivan's Island (north of the bridge). All are within 20 minutes of the city of Charleston, which does not have any beaches.

Some are more abundant than others, this is just a total biodiversity to date. I will update as I collect more.

Gastropods:

Busycon canaliculatum
Busycon carica
Busycon carica eliceans
Busycon sinistrum = contrarium, perversum
Busycon spiratum pyruloides
Costoanachis sp.
Crepidula fornicata
Crepidula plana
Diodora cayennensis
Epitonium angulatum
Epitonium humphreysii
Epitonium multistriatum
Epitonium rupicola
Eupleura sp. - Sharp-ribbed Drill?
Fasciolaria lilium hunteria
Ilyanassa obsoleta
Littoraria irrorata
Nassarius acuta
Nassarius vibex
Neverita duplicata
Oliva sayana
Olivella mutica
Olivella sp. - fossil?
Pleuroploca giganteus - juvenile
Pollia tincta
Prunum apicinum
Pyramidellidae sp. - unknown
Seila adamsi
Sinum perspectivum
Stramonita haemastoma
Terebra concava
Terebra dislocata
Urosalpinx cinerea

Bivalves:

Abra aequalis
Anadara brasiliana
Anadara ovalis
Anadara transversa
Anatina anatina - one valve
Anomia simplex
Argopecten gibbus
Atrina rigida
Atrina serrata
Brachidontes exustus
Chione elevata
Crassostrea virginica
Cyrtopleura costata
Dinocardium robustum
Divaricella quadrisulcata
Donax variabilis
Dosinia discus
Ensis directus
Geukensia demissa
Lioberus castaneus
Lucina radians
Mercenaria mercenaria
Modiolus americanus
Mulinia lateralis
Pteria colymbus
Raeta plicatella
Semele proficua
Sphenia fragilis
Spisula solidissima
Tagelus plebeius
Tellina alternata
Tellina versicolor
Trachycardium muricatum

Others:

Chaetopleura apiculata - chiton
Corambe obscura - onchidorid slug
Cratena pilata - aeolid slug
Doriopsilla pharpa - dorid slug

Gastropods:
Epitonium apiculatum
Epitonium championi

Other:
Dentalium sp.
Armina abbotti