Dear Jeff,
 Hilton Head itself is no place for a sheller.  Good shelling can be found
in the area.  The state park at Hunting Island is excellent if you scout
around.  Its been a decade since we were there but I think you can still
shell there.  The mud flats have some fine angel wings if you don't mind
digging down to your armpit in mud.  Watch out for the oysters, they are
sharp and in slipper mud.