I was in Holden Beach in April. Although I didn't have a NC fishing license, I did take my fly rod for casting practice, and I did take my canoe to scout the intra-coastal waterway side of the island. I've never fly-fished saltwater before, but I was amazed at the number of fish I saw in the marsh areas on the back side of the island. I saw a few that looked well over 2 feet long, likely red drum. There were countless hand-sized fish almost everywhere. There were also lots of surf fisherman and lots of boat fisherman, all in the deeper water of the waterway or the ocean. Most of the surf fisherman appeared to be having limited success at best. I did see one guy flounder fishing from a kayak in one of the man-made harbor areas on the back of the island, and he was having some success.
If I were to go fly-fishing at Holden, I would go to the marsh areas on the back of the island that flood and drain with the tides. The larger shallow areas drain into ditches that wind around for hundreds of yards and create flows just like small streams, except they reverse flow with the tide. They all drain into the intra-coastal waterway. Most of the ditches are less than waist deep at high tide, but they are hard to reach without a boat because the vegetation behind the houses is generally too thick. These fish are in shallow water and are very active, but are also relatively spooky, based on my experience with the canoe.