Mt. Pleasant Pier under the Arthur Ravenel Jr./US 17 Bridge.
Old bridge re purposed in part as a fishing pier. Free to access and views of the downtown Charleston piers are seen. Also container ships and ships going towards the ship yards in the old navy yard pass the pier. Parking is free, but limited. Pier access is free.
http://www.ccprc.com/1171/Mount-Pleasant-Pier