Fonzie's jacket appears to change color throughout the episode. From the start of the episode -- all beach scenes through the beginning of Fonzie's audition -- it is clearly brown. At one point during the audition, the camera cuts away. When it again focuses on Fonzie and Richie, the jacket is now black and remains that way throughout the scene regardless of lighting. Returning to scenes on the beach, the jacket is once again brown.
It is said that the shark is caged underwater, but whenever the shark is seen (in obvious stock footage) there is no cage.