A short answer to “what do sharks eat?” might be "Anything they want to". There's some truth to this, as many types of sharks, though they may have preferences, are opportunistic feeders, sometimes taking on prey much larger than themselves.
Sharks fascinate us, and it is often a fascination mixed with just a little fear or dread. Curiously, we seldom loath the fish, though it can be dangerous to be around them. Sharks are for the most part very attractive fish, they are streamlined and efficient eating machines. Some types of shark, from the human perspective, are killers. We fear the great white shark, the hammerhead shark, the tiger shark, and the Mako shark. All can present a real danger to humans. When we consider these species, the easy answer to "What do sharks eat?” is "People".
Most sharks, even the opportunistic eaters, do not seek out humans. It's more a matter of being in the wrong place at the right time. Most sharks eat fish, at times including other sharks, squid, octopi, and crustaceans. Many are scavengers, and some of the larger and fiercer sharks may take on dolphins, sea lions, and even whales.
Whale Sharks and Basking Sharks - It isn't necessarily true though that the bigger the shark, the more terrible from a human standpoint it is. The two largest sharks, the whale shark and the basking shark are filter feeders. The whale shark is the world's largest shark, and for that matter the world's largest fish, at times achieving a length of over 40 feet, and weighing up to 15 tons. Another filter feeder is the basking shark, the world's second largest fish which often is over 30 feet long. The whale shark gets its name from its size. It is a fish, not a whale. The diet of whale sharks and basking sharks consists of small animals in the water. The sharks swim with their mouths wide open, sucking in large amounts of water, filtering out and swallowing the food, while expelling the water.
Angel sharks - The whale shark and basking shark do not feed on humans, nor other large sea creatures for that matter. The same can be said of the angel shark, which is not dangerous to humans in less you happen to step on or near one. The angel shark is a flat-bodied bottom dweller. It buries itself in sand and mud with its eyes exposed, and pounces on whatever prey happens to venture too close. The angel shark eats primarily smaller fish and mollusks.
Eating Styles - Some of the larger sharks slice away pieces of flesh, others, by shaking their heads back and forth once they have their teeth in to their pray, tear chunks of flesh away. Some species bite and hang on, until the prey weakens enough to be killed or eaten. Some swallow their prey whole.
The Cookie Cutter - In answering the question, "What do sharks eat?", we shouldn't neglect the feeding habits of one rather nasty little shark. It's called the cookie cutter shark. Although it's a cute name, the cookie cutter shark specializes in taking small chunks of flesh from its prey, much like one would take a scoop of ice cream from a container. The cookie cutter digs in with its upper teeth, then slices the flesh away with its lower teeth. It feeds mostly on much larger bony fish. Most cookie cutter species grow no larger than a foot in length, though some species approach 6 feet in length.
As you can see, the diet of sharks is quite varied, as are the types of sharks. None look at humans as a food of choice, though some eat anything that comes within range. Most shark attacks are not fatal. The great white shark is the most notorious as far as attacking humans is concerned, while the angel shark, basking shark, and whale shark could be considered harmless. The cookie cutter shark is probably harmless too, though I wouldn't wade out in water if one was around.