I just got back from a week in Myrtle Beach (7/26--8/2) and did 6 dives with Express Watersports out of Murrell's Inlet. I did the Bill Perry, 11 Mile Tugboat, and Goldfinch Reef.
Temps were 73-77 at about 65 feet and visability went from 5 feet to 15 feet. They said the last hurricaine stirred everything up and messed up the viz.
It was still a good bunch of dives. The dive and boat crew is good and take care of you. Just a word of caution if you get seasick. We had 3-4 foot swells out over the wreck sites that became a problem for some when the boat tied up to the wreck and stopped moving forward. 2-3 people got sick on each of the trips I was on. I'd suggest taking motion sickness meds if you even remotely think you might be prone to getting sick.
The boat rides were either 1hr 15min (Bill Perry and Goldfinch), or 45 min for 11 mile. We left at 0730 and were back on the dock by 1:30 or 2:00 each day.
I would suggest checking ahead of time to make sure enough divers have signed up for the dives you want to do. I had signed up for the BP-25 dive but they cancelled it the night before due to lack of people signed up. They did call me the night before to tell me, but I would have liked to know the dive was in danger of being cancelled ahead of time so that I might have had a chance to book with another operation. Not a huge deal, but something to think about.