Intertextuality: is a term to describe the visual referencing between films; the films 'borrow' from each other. They borrow certain camera angles, mise en scene, snippets of sound or editing methods. They change these aspects a bit so it is not exactly the same.
Physco was released in 1960, and directed by Alfred Hitchcock, it is often classed as a 'complex physiological thriller'; it has even been named "The "mother" of all modern horror suspense films". Other films have borrowed aspects of this film, and more importantly from the famous shower scene clip.
What Lies Beneath: Has borrowed aspects from Physco, this film also introduces a shower scene to us. The bathroom is white and pure, just like in Physco. Also, the Blonde damsel in distress is the person who is in the shower/bath, which is also another aspect of Physco. The high angle shots onto the Blonde female were shown in both clips and is another aspect that What Lies Beneath has borrowed from Physco.
Succubus: This student thriller takes the shower scene from Physco but they add an interesting twist to it; they use the entire scene. But instead of having the Blonde female as the victim, she is actually the murderer. They use the turning on of the shower CU that Physco uses, this particular shot adds suspense because in indicates that something isn't quite right. They took many of the camera angles from Physco, they used the same stabbing in the shower technique and the CU of the dead body; however Physco used an ECU of the woman's eyes and Succubus used an ECU of the mans toes.
Both What Lies Beneath & Succubus borrowed a few of the strengths from Physco to add to the success of there film, however they took these strengths and made them there own.