Terry Kiser (Bernie)'s stunt double suffered a few broken ribs during filming due to all the pitfalls and stunts of playing a dead man; most notably in the scene involving 'Bernie' being dragged around the surface of the ocean, bumping into metal floating obstacles.
Bernie's house is a real home on the south end of Figure 8 Island near Wilmington, NC and still remains. Many of the movie's scenes were filmed in this area including the waterway at Wrightsville Beach, and the dock and lighthouse scenes at Bald Head Island about 30 miles south.
Richard suggests they go to Jones Beach with all the syringes. This is probably in reference to the infamous "Syringe Tide" in 1987-1988 when medical waste washed up on several beaches in New York/New Jersey, costing massive losses in tourist dollars.
After Richard knocks out the man that Bernie fired, he informs Larry "You can come out now Rambo." First Blood (1982), the first Rambo movie, was also directed by Ted Kotcheff. The gardener in the film (George Kee Cheung) wears a costume similar to the one in Rambo: First Blood Part II; he was the film's villain.
Catherine Parks (Tina) and Terry Kiser (Bernie) are both Friday the 13th series alumni. Parks starred as Vera Sanchez in Friday the 13th Part III (1982), and Kiser appeared as Dr. Crews in Friday the 13th Part VII: The New Blood (1988).