Scott,
Theres two charter ops down there. One is Coastal Scuba, however I think they ended their season at the end of October. The other is Express Watersports. They are located in Murrels Inlet. I have dove with Express this past summer and they are great. It looks like they only have one dive when you are there; the Bill Perry on the 26th. You can check them out at www.expresswatersports.com. The Bill Perry is a pretty good dive usually. There really isn’t any shore diving that I know of thats worth doing. Pretty crappy viz and nothing to see. Theres also another shop Nu Horizons right in Myrtle. Their website is southcarolinadive.com but I think they are more of a group charter type but you might want to check because sometimes I think a group of people book a charter and its not all the way full.