The sister's house appears to be in normal condition when they arrive, but an insert shot shows the house with broken window glass and chipped paint that have been digitally added.
The scenes where Gail is partially buried on the beach contain two plot holes. First, the damp sand over her wasn't deep enough to prevent her from freeing her arms and digging herself out. Second, the rising tide would have taken hours to reach the point it did instead of the minutes shown. This time delay could have meant Gail's discovery and rescue.