For the scenes in which the shark attacks people in the water, dummies or models were often used to represent the victims. These dummies were made from a variety of materials, including foam, rubber, and silicone. In some cases, real human limbs were used in place of the dummies.
For the scenes in which the shark attacks people on land, special effects were employed. These effects included the use of fake blood, animatronic sharks, and computer-generated imagery (CGI). In some cases, actors were filmed underwater and then composited into scenes with the shark.
The combination of these techniques allowed the film crew to create the illusion of people being eaten by the shark without actually harming any humans.