5 Most Dangerous Contests

Vertical Blue

Free diving is a sport that's quickly grown in popularity in recent years. Diving in beautiful water without oxygen tanks -- that's the free part -- can be an exhilarating experience. Some free divers compete to spear fish while others simply engage in a contest to see who can stay under the longest. Still others participate to see how deep they can go. Enter the Vertical Blue competition.

Vertical Blue draws the best free divers in the world to a serene, clear blue underwater cavern in the Bahamas. One by one, the divers descend down a rope that extends more than 600 feet (182.9 meters) below. They have to fight against the impulse to breath, they risk blacking out under the strain, and they even have to be prodded to inhale and exhale once they return to the surface -- such is the state of delirium they find themselves in once they're again in their natural environment [source: Kennon].

But, perhaps more than anything, they have to resist the overwhelming anxiety that can sweep over the human body once it's hundreds of feet below the surface and desperate for oxygen. Passing out is common at the competition. Most participants are familiar with the unpleasant experience of losing consciousness and being pulled from the water. Most also know of someone -- a fellow diver -- who never regained consciousness after pushing their limits in the deep blue [sources: Kennon; Cochrane; Nipps and Tomalin].