We know that the most attacks we have from sharks come from few species, like great white shark, tiger shark and bull shark (yes that shark which we can find it even in rivers and lakes).
But have you ever made questions, like why is it happening that?
First of all, to note only few sharks of the 500+ species attack humans.
Now i will show you below macro photos of two species teeth, from the great white shark and from the tiger shark.
As you can see in the photos, the teeth are sharp, serrated and shaped in that way that can cut raw meat, because they hunt seals, sea lions, turtles, dolphins, whales and other big marine animals.
That's why even when they use the "try bite" method to humans to see what we are and if we are edible we have lot of accidents and deaths. Because their jaws have a lot of strength and our body skin, muscles and bones are weak in comparison of the strength their sharks jaws have with those teeth.