Because they are not inhaling pressurized air underwater, free divers are not at risk of decompression sickness (the bends). They just take a breath of air at the surface, descend, and return to the surface with the same breath. Things simply return to normal. There is no need for a decompression stop on average depth dives.
The only real danger for free divers is getting caught in a current. If you go deep enough, you will reach currents stronger than those on land. The best way to avoid this problem is by staying within your limit. Don't go deeper than you feel comfortable or can handle if you get into trouble, bring someone who knows how to rescue you out, and then come back when things are safe again.
Free diving isn't really possible anywhere except maybe near shore or in very protected waters because there's nothing to prevent you from being swept away by a current or having something fall on you while you're down there. Free diving in open water where you could be hit by a boat or dragged down by a large object is not recommended.
There are different ways to become a free diver. You can either learn how to swim properly with help from an instructor or by practicing in shallow waters before going all the way out or you can even buy a kit that includes weights you wear around your neck that help you stay down lower pressure areas.
The body's natural CO2 level is around 0.04%, so only very low amounts of this gas are needed to prevent bubbles from forming in blood vessels and tissues.
The main danger for free divers is the effect of water on their lungs. Because they are not breathing air that has been compressed by pressure, free divers must constantly adjust their buoyancy to stay submerged. This means that their bodies are always exposed to the pressure of water, which over time can have serious consequences for their health.
Free diving is not recommended for people with lung diseases such as emphysema or bronchitis. Free divers who smoke should know that it increases their risk of developing lung problems. Divers who use drugs or drink alcohol excessively should also be aware of the effects of these substances on their lungs.
People who free dive should learn how to control their depth so they do not go too deep or stay down too long. This is because excess pressure damages tissue cells, just like when you push them too hard when exercising. Over time this can lead to severe lung disease if the pressure is kept up continuously.
Often called "the bends," decompression sickness happens when a scuba diver ascends too quickly. Divers breathe compressed air that contains nitrogen. At a higher pressure under water, the nitrogen gas goes into the body's tissues. This can cause pain, paralysis, and even death.
The problem is that any tissue in the body is damaged when it comes out of the water, no matter how short a time it has been submerged. Tissues closest to the skin are affected first because they're exposed to the air while those deeper within the body are protected by other tissues. The brain and spinal cord are particularly vulnerable because of their distance from the surface. Even if a diver does not suffer any immediate effects from the bubbles, more serious problems may develop as the body attempts to repair the damage.
The deeper a dive, the longer a diver can stay underwater before needing to come up for air. But there is a limit to how deep a diver can go. If the pressure at that depth is greater than about 1.1 times the diver's absolute pressure, then bubbles will start to form in the blood. These bubbles would then rise through the blood to the lungs where they could cause problems upon resurfacing.
To prevent the buildup of excessive pressures at great depths, diving regulations require that divers ascend at a safe rate.
You cannot receive any oxygen if you simply breathe inert gas. Deep divers may use a combination of oxygen and helium to avoid the "bends" in some instances. The bends occur when divers ascend too rapidly, causing dissolved nitrogen to form bubbles in their blood and cause embolisms. To prevent this, they are given an initial dose of oxygen at high pressure so that it enters their bloodstream before they go down again.
Oxygen is vital for life because it reacts with hydrogen molecules to form water, which is essential for living organisms. Without oxygen, humans would die within minutes. However, due to its reactivity, much of the oxygen we breathe in is lost through exhalation. This is why airliners need to constantly pump pure oxygen into the passenger cabin from outside sources - otherwise everyone would die!
The most common source of oxygen for deep divers is compressed air, but they can also use nitrox (80% oxygen + 20% nitrogen) or heliox (hydrogen oxide, a mixture of oxygen and helium). These gases are mixed on site by equipment called compressors. They work by taking ambient air and pushing it through metal plates coated with titanium or platinum which absorbs the carbon dioxide while letting out harmless nitrogen and other gases. The divers can then breathe these purified gases instead.
Deep diving brings with it many risks not present in shallow diving. The pressures involved can burst blood vessels or even damage the brain.