The movie's tagline "Just when you thought it was safe to go back in the water . . . ", became one of the most famous and popular taglines in motion picture history. The blurb has frequently been spoofed and referenced in both social vernacular and in other movie promotions as well.
Marc Gilpin (Sean Brody) claims that when they were shooting one of the scenes on the makeshift raft of wrecked yachts, they were being circled by a real hammerhead shark. The actors were scared and began to scream and holler at the production crew, which was filming that particular scene from a distance. The crew was oblivious to the danger and assumed the actors were simply "in character" and gave them the thumbs up.
Roy Scheider did not originally want to appear in this film, but had recently left the production of Voyage au bout de l'enfer (1978), which led to conflicts with Universal Pictures, with whom he was locked into a multi-film contract. The studio agreed to forgive his leaving Voyage au bout de l'enfer (1978) if he did this film, which they would count as the two remaining films of his contract with them. Scheider agreed to the terms, but was resentful of his involvement from the outset and clashed frequently with director Jeannot Szwarc.
On the Brody's front porch is a flower planter painted bright yellow. It is one of the barrels from the first Les Dents de la mer (1975).
The name of the small rocky island with an electrical relay station on it was "Cable Junction" island. This was actually a set that caused numerous problems during filming. The island was made from plastic / fiberglass material and was set on two barges. The surface of it was so slippery it was difficult to traverse it or even grab hold of it. This resulted in numerous retakes having to be shot, with actors slipping and falling off it constantly. Due to not being anchored properly, it once drifted away into the ocean, and the production had to go out and tug it back. In The Making of 'Jaws 2' (2001) DVD documentary, director Jeannot Szwarc recounted the day when he was informed that his island set was "on its way to Cuba".