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Scuba Diving Risks


Wouldn’t it be great to have gills? Fish pull the oxygen they need out of the water. They don’t get the bends, no matter how long they stay under. We, on the other hand, have lungs, and must carry down breathing gas and a delivery mechanism (tank and regulator). We are in a foreign environment and dependent on our gear, our training, and our judgment.

If you’re reading this as someone considering diving, know that all of these concerns will be discussed and defused in your Open Water Diver course. There are risks associated with our gear. There are risks associated with forgetting or ignoring your training, such as not monitoring your gas supply. And there are risks we sometimes choose to add, such as going deep. Please remember that this is a discussion of risks, not a complete inventory.

Gear-Related Risks

If some part of your tank (scuba cylinder) or regulator fails during a dive, you could exhaust your breathing gas. Regulators must be serviced and tested annually, with parts replaced on a regular basis. Tanks are inspected annually, and stress-tested for their integrity every five years. And your dive buddy should always be within reach, to allow the two of you to share air while you surface.

If you somehow lose your mask, you’ll be unable to focus on anything underwater. Again, your buddy is there and prepared to link up with you to make a safe ascent. Salt water is actually quite close to the body’s own salinity, so ocean water is usually more pleasant to the eyes than chlorinated pool water.

Other possible gear problems include failure of the BC (buoyancy control jacket) and failure of your dive computer. Again, the buddy system can deal with these problems. But note that modern scuba gear is so good that dive-related injuries are very seldom due to equipment failure.

Dive shops, dive boats, and dive resorts must carry quality items and maintain them well, or they quickly go out of business. When renting gear, it’s smart to ask when it was last serviced. When you own your own gear, you’ll want to keep track of service dates from year to year to keep it in top condition and maintain the warranties.

Avoidable Risks

Most of the risks of scuba diving can be avoided by following proper procedures before and during the dive. Your training is in large part learning and practicing those procedures until the skills are second-nature. We’ll start with the most serious risks and work our way down.

Drowning: Running out of air underwater, losing the regulator from your mouth and being unable to replace it, or being unable to keep your head above water once on the surface can be lethal.

Decompression Sickness: Ascending too quickly after diving can cause nitrogen, dissolved in your tissues, to form bubbles. This is also called “the bends” and can result in symptoms ranging from a mild skin rash to unbearable pain. The deeper and longer the dive, the more severe the bends can be.

Over-Expansion Injuries: Holding your breath while ascending can cause the air in your lungs to expand and force its way out. Depending on the failure mode, air can be trapped in the chest cavity, causing chest pain or shortness of breath, or air can travel into the arterial blood, causing an embolism, which can be fatal.

Nitrogen Narcosis: The deeper you dive, the more the nitrogen in your breathing gas acts on your nervous system like an anesthetic, dulling your thought processes. Going deeper than you’ve trained can lead to poor decision-making and can be fatal.

Heart Attack: The demands of carrying gear, entering the water, and coping with waves or currents can lead you to over-stress your heart. This can be fatal if you’re not in proper physical shape.

On-Board Injury: The necessary extra care required to stay safe on a boat is compounded in scuba by the equipment you’re assembling, donning, and carrying on and off the boat. Tanks and weights in particular require safe stowing.

Hypothermia: If you do not have proper thermal protection, the water may draw enough heat from your body to weaken you and slow your thinking and reflexes enough to kill you. Hyperthermia (getting hot to the point of injury) is possible on the boat or shore if you have no shade.

Dehydration: Breathing the extremely dry air of scuba tanks, combined with exertion and warm-climate exposure, tends to dry out the body. Failure to drink enough water can be severely debilitating.

Bad Air: The gas in your scuba tank can be contaminated, for example with traces of oil, if the filters used in compressors and fill equipment fail. Tank air should be completely dry and odor-free.

Lost at Sea: Ocean divers may encounter currents that prevent them from returning to their boat, or waves on the surface that prevent them seeing the boat (and the boat seeing them). Diving in current requires special planning and techniques.

Ear Injuries: Failure to equalize your eardrums while descending can bruise or rupture them. Frequent diving which keeps your outer ear canals damp, or diving in contaminated water, can cause ear infections such as swimmer’s ear (otitis externa). Middle and inner ear injuries are also possible from actions such as late and too-forceful equalization.

Bumps and Scrapes: failure to control your position underwater can result in contact injuries (stings, cuts) with rocks or living organisms, such as sea urchins. Over-exertion or sudden moves can cause cramping. Surf, swell, and strong currents can carry you into rocks and knock you down while coming ashore.

Risks We Choose

Sometimes we decide that the rewards are worth taking the risks. Here are some dive-related risks that are sometimes undertaken voluntarily.

Health Conditions: It is your responsibility to assess your own fitness to dive, both physical and mental. Diving with congestion (such as from the common cold) can cause sinus headaches, bloody noses, and much worse. There are diabetics who choose to dive but take special precautions. Some medical conditions are serious enough to make diving unacceptably risky (a seizure disorder, for example).

Overhead Environments: Venturing into caves or wrecks carries great risks. Anything that delays your return to the surface can cause you to run out of air. Losing your way or disturbing fine bottom sediment to the point of losing all visibility are very real possibilities. Entanglement is also a great risk in wrecks.

Sharks: Diving in the vicinity of the more aggressive shark species or on special “shark dive” outings, is choosing some risk. Most ocean diving is done in relatively shallow reef systems, where sharks are rare and generally seen at a distance, cruising in deeper water.

Deep and Dark: Venturing beyond the conditions in which you were trained, and the limits of your comfort zone, carry the risk that your planning, skills, or decision-making are inadequate to the new challenges.

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