Fort Wagner sat on the western beach of Morris Island, south of Charleston, S.C. Union forces attacked from the southern tip of the island, because another fort, Battery Gregg, defended the northern tip. Therefore, if attacking northward, the ocean should be on the 54th Massachusett's right. Instead, it's on their left, and the swamp is on their right. Besides the fact that a previous assault on Fort Wagner had already taken place before this charge, someone probably got a good smack for such an error in a historical movie.