Screech uses scuba gear to hide in the pool and secretly take pictures of the girls' swim team. However, when he reports to Zack afterward he's still wearing the gear but is completely dry.
Screech is supposedly taking underwater pictures of the girls swimming secretly, yet their cutouts reveal they are posing on land and completely dry.
In last scene in Kelly's bedroom, as the shot moves from Kelly to Zack, a moving camera is reflected in a mirror just behind Zack for a few seconds.
At the beginning, before Zack appears, the boom mic is briefly visible in the top right corner of the screen.