Luxury waterfront homes often promise private docks, sweeping river views, and resort-style pools. This Mount Pleasant estate has all of that — but its most remarkable feature sits behind a different set of doors. Listed for $5.975 million by Kimberly Youell and Roddy Matthews of Coldwell Banker Realty, the 11,211-square-foot residence at 4145 Colonel Vanderhorst Circle includes a purpose-built,...