Julie, I have been diving in Myrtle Beach. In fact, I went over this past summer there. There isn’t any shore diving anywhere so you’ll have to go out on a charter. The thing is there are only two: Express Watersports and Coastal Scuba. However it is a pretty good drive to get to Coastal. I dove with Express and was very pleased. Their crew was very nice, helpful, and friendly. I look forward to diving with them each year I am down there for vacation. Their website is expresswatersports.com. As far as dive sites Express offers a variety with charters running daily through the summer. I dove 18 miles off the coast of Murrels Inlet at a site called Goldfinch. Viz was about 30 feet. The bottom was a little stirred up due to a storm the night before. On the website it has all locations they go to. Youtube was also helpful I just searched Myrtle beach scuba or the dive site name and watched some videos to pick the site I wanted to dive.
PS: They also got a very nice boat