Scuba diving is a wonderful sport. Underwater you experience an amazing variety of plant and animal life, physical and sensory effects, and an overall environment that simply isn't possible topside. But scuba diving has serious and real risks. With proper guidance and training, those risks can be minimized easily in order to enjoy all the positive aspects.
One of the most serious potential risks comes from nitrogen narcosis. This is a condition that can result from diving too deep, bringing on disorientation, euphoria, errors in judgment and even hallucinations or unconsciousness. This can be fatal.
Though the exact cause isn't known with certainty, scientists hypothesize that the way pressurized nitrogen enters the nerve cells leading to the brain is the likely culprit.
As a scuba diver descends, water pressure increases - 1 atm for every 33 feet (10m). By design, a regulator - the device that allows air to be drawn from the tank for breathing - compensates and delivers gas at the ambient pressure. The air breathed is at the same pressure as the surroundings. That's needed in order to help the lungs expand.
But when that compressed air, containing nitrogen, enters the bloodstream through the lungs, odd things can happen - including some of the symptoms listed above.
At about 100 feet (30.5m), the effects of nitrogen narcosis begin to be felt by the average scuba diver. But since 'average' varies from person to person, it can be felt sooner or later, depending on the individual's overall health and training and recent activity before diving.
At whatever exact depth the condition occurs, it is inevitable for everyone. At around 300 feet (91m) - though it can occur higher - there will be serious impairment of motor function, hallucinations or unconsciousness.
The effects are reversible, but once you lose good judgment it's difficult to perform a proper ascend in order to avoid the opposite problem - decompression sickness.
Training can influence the precise depth, but it can't entirely eliminate the result. Fortunately, it's easy to avoid nitrogen narcosis and its ill effects.
Always buddy dive and keep your partner in view. Work out in advance a system of testing for good mental and physical functioning. One common technique is the 'thumbs test'. One diver raises two fingers and the other raises two fingers and a thumb in a simple test of arithmetic. Two plus one equals three. This is slightly more complicated than simply copying the number of fingers raised and so shows some elementary reasoning ability.
Since you have to be close to your diving buddy to perform the test, it's possible that both are affected. By that time the trouble has already started.
To head difficulty off at the pass, keep an eye on your gauges. Always dive with a depth gauge and get into the habit of checking it periodically. Stay well above the danger zone unless you have special training and equipment. Don't let your recreational dive, part of an adventurous vacation, turn into an occasion to visit the hospital or worse.