The house, barn, and lake were all purpose-built on location. The man-made lake wasn't properly sealed, and, subsequently, the water drained into the soil during the first week of filming.
This was the first of the Friday the 13th films to use the iconic hockey mask, which has been in every sequel since.
The Royal independent movie theater in Toronto, Canada, which closed in 2006, had owned one of the few copies of the movie in its original 3D format. They used to screen the film once every Halloween.
The original plan for the film involved Ginny (Amy Steel) from the previous film being confined to a psychiatric hospital. Suffering from the trauma inflicted on her during the ordeal with Jason, she eventually finds that, intent on revenge, he has tracked her down, and he begins to murder the staff and other patients at the hospital. Steel ultimately declined the offer to return to the series as she was busy with other projects, but has since said that she thinks she should have accepted.
To prevent the film's plot being leaked, the production used the fake title "Crystal Japan," after a David Bowie song. This began an on-again, off-again tradition of giving "Friday the 13th" films David Bowie song titles during filming.