There is a scene towards the beginning during which a license plate is removed from a "tiger shark's" mouth. From a biological standpoint, a tiger shark's tail fin is not symmetrical from top to bottom. The top part of the fin is elongated. Also, the teeth of a tiger shark are wide, serrated, and curve towards the back of the mouth. The tiger shark in the movie has a symmetrical tail fin and its teeth are smooth, thin, and pointed. Essentially, it has all of the characteristics of a Mako Shark (the other sharks in the movie). Not to mention the fact that tiger sharks have a broader head and do not have stripes once they grow out of the juvenile stage.