The shark has changed little in more than 300 million years in the earth's oceans. Classified as fish (Pisces), sharks are among the oldest creatures on our planet.

Sharks differ from most fish because their skeletons consist of soft, flexible cartilage instead of bones.

While the cartilage enhances a shark's swimming ability and makes it more edible, it offers little support for the shark's internal organs out of water. Just a few minutes out of water will give the shark a fatal injury.

Sharks must also swim continuously to stay afloat because they don't have the air-filled swim bladder found in other types of fish. Most top-swimming sharks must also continue moving to obtain the oxygen necessary to stay alive.

Sharks are considered to possess a low level of intelligence by many experts, but their indifference to injury is well-documented and their sense of smell is extremely keen.