Worn by: Richard Dreyfuss as Matt Hooper
Reference: Alsta Nautoscaph
Brand: Alsta
Oceanographer Matt Hooper wears an Alsta Nautoscaph Superautomatic throughout the film—a true deep-cut timepiece that was debated online for years before being definitively identified. The watch features a distinctive bicolor bezel with dual minute and hour indicators, cushion case, and unique bracelet. Hooper strikes as the kind of guy who would intentionally not wear a Rolex, instead feeling compelled to be different. The Alsta brand folded in the late 1970s but was resurrected in 2014, releasing a near 1:1 recreation of the 1975 Jaws watch in a fitting 1,975-piece limited edition in 2020. The watch is clearly visible during the dinner scene where Hooper explains the theory of territoriality to Chief Brody.

Source: https://www.hodinkee.com/articles/two-diametrically-opposed-watches-head-for-open-water-in-jaws
Worn by: Roy Scheider as Martin Brody
Reference: Hamilton Lyndon
Brand: Hamilton
Police Chief Martin Brody wears a rather unassuming gold-filled Hamilton Lyndon CLD throughout the film—a watch that couldn't be more different than Hooper's dive watch, or any less appropriate for a law enforcement officer whose primary jurisdiction involves a lot of water. The 34mm watch features applied Arabic numerals and striking case lug design. While less exciting than the tool watches enthusiasts obsess over, it speaks to Brody's everyman quality and the reality that brands like Bulova and Hamilton ruled the day in the 1970s. The watch gets nearly 10 full seconds of screen time during the knot-tying scene where Quint judges Brody's rope work in open water.

Source: https://www.hodinkee.com/articles/two-diametrically-opposed-watches-head-for-open-water-in-jaws