In the movie "Risky Business" Joel Goodson sinks his father's car into Lake Michigan. What type of car was this?

Although Risky Business (1983) is not a car movie, there’s more than a few quintessential moments in the film where the Porsche 928 has a major role. But this movie itself is still one with a simple premise. Joel Goodson (Tom Cruise) is a high school senior whose parents leave home for a week-long vacation. While they are away, Joel engages in loads of teenage hijinks. The culmination of his shenanigans result in him transforming his parent’s suburban home into a brothel. It is every vacationing parent’s worst nightmare.

One of the film’s subplots revolves around a 1979 Porsche 928 owned by Joel's father. At the beginning of the film, Joel’s father has specifically forbidden Joel from driving his 1979 Porsche. But of course this is one of the first things Joel does after his parents leave the house. Soon thereafter, Joel gets into a major car chase with a “killer pimp” named Guido, and eventually Joel sinks the car (Porsche 928) in a well known Great Lake. When a dock on Lake Michigan collapses, the car goes into the water. It seems that Joel once was the model son who had been good too long.