Sharks are fierce predators, but they are very cautious. If they weren't cautious, they wouldn't grow so big. Sharks are usually very picky about what they eat. They often eat fish, especially fish that may be injured or sick and that are easier to catch. But they are wary of other things in the water, and often have to be lured close to scuba divers by using bait.
Sharks patrol the waters above and around the reef.
Some sharks, like this Caribbean Reef Shark, are fast enough to catch the reef fishes that can maneuver and hide in the reef quickly. Many types of larger and dangerous sharks aren't fast enough to catch reef fishes, and are seldom seen near tropical coral reefs. Many species of sharks are similar, and often are hard to tell apart. Note the black tips on the undersides of this shark's pectoral fins. Sharks are fairly intelligent, and have been compared to dogs or cats.