We are looking for an affordable resort on or near the water in the Carolina's for a wedding ceremony and reception for about 100 people.

I have to say that affordable & resort, really don't fit together all that well. You're more likely to find what you are looking for in SC. Wild Dunes, perhaps.

We might need more info on your degree of affordability. And the time of year. The daughter of a good friend was married in the Pawley's Island chapel (which is a bit funky, but was perfect for this group). It backs up to the marsh and the back of the chapel is a window that looks out on the marshes. The seats are old theater seats.
The reception was at the Litchfield Plantation beach facility. It was very lovely.
There are hotels and motels in the area for lodging, as well as Litchfield Beach and Golf Resort.

Thank you so much for your suggestions. We did see Wild Dunes, it was very nice but pricey. We are seriously looking at the Litchfield Resort. My daughter is vacationing in Myrtle Beach next month and is going to check things out for us. I appreciate the input-- I had not found The Litchfield Resort in my own search!

I'll second Pawley's Island and Litchfield... we've had a family place there for years and it is beautiful, laid back, and fun. Litchfield Resort will have beach front options, but you may want to look into Litchfield Plantation- beautiful setting, on the marsh... best of luck!

Yes, Litchfield Resort does have a small beach house/club. I had sort of overlooked that as a possibility in and of itself. It is right next to our place there.
Litchfield Plantation is different, but also has a beach club on Pawley's Island. The Plantation itself is not on the beach--BEAUtiful original plantation house with a restaurant facility next door. I don't think this would be a very economical possibility as well as not being on the beach.