We get this question a lot, so we thought we'd make the answer available for every one. This is one of those fun, but hard to answer questions because there is no easy answer. So, here is a short and long version. Some sharks may hunt dolphins, some dolphins may hunt sharks.
Predators usually hunt the ill, injured, old or young because they're easier to catch.
First, let's be sure you know a few bits of information first. There are 350 different kinds of sharks. Most do not hunt an animal as large as dolphins. If sharks are in the vicinity of dolphins they generally ignore each other. Predators, like sharks, often sneak up on the prey.