When Mary and Grace dance after leaving the pool, Graces' gray towel changes positions from around her bust to around her waist several times.
When Grace rubs sunblock on Mary's back, Mary's hair is full and partially covering her right ear. In a different shot, Mary's hair is not as voluminous and is clearly tucked behind her right ear.
When Grace is applying sunblock to Mary's back, Mary is lying completely flat on her stomach with her arms forward and her hands beneath her chin. In successive shots, Mary is propped up on her forearms then back to lying flat again.
Toward the end of the movie, the knife wounds inflicted in Tom's chest, by Mary, change between scenes.
When Grace changes to a 2 piece black bathing suit her hair is dry, in the next shot and before she jumps into the pool her hair is all wet.
Toward the end of the movie, Mary applies a small towel to Tom's chest wounds. The towel absorbs none of the blood.