I assumed this was Figure Eight Island, which is on the opposite side of the channel from the northern tip of Wrightsville Beach where Shell Island Resort is. Source on IMDb and elsewhere claim it is at Shell Island Resort, but it’s not—or maybe it is. I don’t know, there is a lot of conflicting information. It’s near, but you can’t access Figure Eight Island anyway as it’s private property, so it’s the closest you can get in public areas.
I did some digging on this and found a wonderful article written up which explains so very much more than I could have hoped, and provides real amazing information such as that the production built the house from scratch for this movie, but only half of the house. The two following photos are from someone named Mike who provided it to the
This is similar to how Under the Dome build a house which catches fire, but it’s only a façade with walls missing and no insides. At least with this structure in Sleeping with the Enemy, the interiors were within the half of a house.
According to the article linked above, the production demolished the structure and removed all traces of it once the production was completed. What I do know from living in this area a while is that at one time the ocean was hitting Shell Island Resort when the tide came in, and it was closed until a dredging operation could be done to rebuild the northern end of Wrightsville Beach. I remember going to the roundabout and the channel waters were feet from the road. Now, it’s extended outward quite far and the Shell Island Resort is open again. With that said, the area that they build the structure could have turned in to the channel at some point.