Unprovoked shark attacks on humans are rare, but they do occur, and there are ways to reduce your chances of becoming a victim.

Such attacks, most of which occur near shore or near steep drop-offs, fall into three major categories:

1. Hit and Run
By far the most common type of shark attack, the "hit and run" usually occurs in shallow waters or surf zones, with swimmers and surfers as the victims. In a hit and run, the shark inflicts a single bite or slash wound and then speeds away without returning. The resulting injuries are usually small lacerations, often on the leg below the knee, and seldom life-threatening. It's believed this kind of attack is frequently the result of the shark confusing the human for prey, such as a seal or sea lion.

2. Bump and Bite
The less common "bump and bite" attack usually occurs in deeper waters with swimmers and divers as the target. In a bump and bite, the shark initially circles and then bumps its victim. With the bump, the shark's electroreceptors confirm that the object is alive and thus potential prey, triggering the shark to bite, sometimes repeatedly. The resulting injuries are usually severe and sometimes fatal.

3. Sneak Attack
Also less common than hit-and-run attacks, the sneak attack usually occurs in deeper waters involving swimmers or divers. In a sneak attack, the shark lunges without warning, usually from below the victim, and bites, usually repeatedly. The resulting injuries are generally severe and often fatal.

Courtesy: The International Shark Attack File Web site, maintained by George Burgess, University of Florida Museum of Natural History, Gainesville, Fla.

OK, now that you're familiar with the kinds of shark attacks, see if you know how you can reduce the risk of one.