The maximum depth restriction for recreational diving is 40 meters (130 feet). A dive deeper than 60 meters (200 feet) is referred to as a “deep dive” in technical diving. A deep dive, as defined by most recreational diving organizations, permits you to drop to 18 meters and beyond.
The reason for this limit is that at depths greater than 20 meters, blood oxygen levels begin to fall off sharply. At certain points during the dive, your brain receives less oxygen than it needs which can lead to dizziness, confusion, and possibly black out. The risk of injury increases with depth so limiting yourself to 40 meters ensures that you will not go any deeper if safety is important to you.
Below 20 meters, divers use special equipment to provide breathing air. At these depths, the amount of time it takes for enough oxygen to be absorbed into your bloodstream is too long to be effective without mechanical assistance. The two main methods used by deep divers are mixed gas diving and hyperbaric oxygen therapy (HBOT). Mixed gas diving involves using different percentages of oxygen and helium in the breathing mixture while hyperbaric oxygen therapy uses pure oxygen at elevated pressures above 1 atmosphere.
Mixed gas diving is usually done in concentrations of approximately 21% oxygen and 79% nitrogen (or 30 meters underwater). This allows sufficient oxygen levels for activity but does not cause pain or irritation due to the high pressure.
Deep diving for scuba divers refers to diving below the depth of 18–20 meters (60–66 feet), which is the maximum depth at which freshly qualified scuba divers may dive. In truth, a genuinely deep dive is deeper than 30-35 meters (100-115 feet), which is the depth at which the next level of scuba diver certification allows you to dive.
The human body was not designed for such depths. The pressure at 20 meters (66 feet) is about one-third of what it is on Earth’s surface. It takes less than 10 minutes for blood to be forced out of the capillaries into surrounding tissues. At these pressures, even small amounts of carbon dioxide dissolved in blood can cause severe pain and neurological damage after only a few minutes. To avoid this problem, scuba divers use special equipment for breathing gas under pressure.
The human body is very adaptable, though, and most people can adjust to living at such depths for several days. Some species of fish, however, have evolved with these pressures constantly changing. For example, the anemone fish has large muscles attached to its spine that help it resist pressure changes while swimming in its environment. Humans do not have anything similar because we do not swim, but research shows that staying down for several days may give our bodies time to heal itself of any injuries caused by high pressures.
That indicates that most individuals can safely dive to a depth of 60 feet. Most swimmers will only free dive to a depth of 20 feet (6.09 meters). When exploring underwater reefs, experienced divers can safely dive to a depth of 40 feet (12.19 meters). When diving in cold waters, people should avoid going deeper than their body weight plus 15 degrees Fahrenheit (minus 9 degrees Celsius).
The average person weighs about 150 pounds (68 kg), so for safety’s sake, they should not go any deeper than one-half their body weight plus 15 degrees F (9 degrees C). If the person weighs 200 pounds (91 kg), then they should not go any deeper than one-third their body weight plus 15 degrees F (9 degrees C).
The main danger of diving deeply is running out of breath before reaching the surface. At high pressures like those found at great depths, there is less oxygen available per volume of air, so even small errors in breathing can cause oxygen deprivation and unconsciousness. On average, humans can stay under water for about 10 minutes before running out of breath. But some people may be able to go longer because of their greater fitness or experience. The record holder for deepest human immersion is Sue van den Berg, who on May 12, 2010, lived under water for 4 minutes 43 seconds while taking part in a demonstration for a television show.
The answer to the question “how deep can you SCUBA dive?” for recreational diving is 130 feet. Proper certification is strongly advised for those SCUBA diving depths. The maximum depth you may dive as a beginner open-water SCUBA diver is 60 feet. No special training is required to be able to dive up to 30 feet, but some specialty courses may include this capability.
As far as safety is concerned, the deeper you go underwater the less oxygen there is in the blood and tissues of your body. This is called hypoxia and it can cause serious problems if it goes untreated by bringing about cardiac arrest or brain damage. So the safe limit for diving is determined by how long you can stay under water without getting any air into your lungs (known as your “air limit”). The more experienced you are, the more likely you will be to know when you are approaching your air limit. If you feel dizzy, exhausted, or experience pain in your arms or legs, you should come back up immediately.
For beginners, however, it’s best to err on the side of caution and not go too deep. You will need to spend more time under water, which reduces the amount of time you have to spend above water enjoying life. But that doesn’t mean that you shouldn’t ever try to dive deeper than 60 feet; only you can decide what level of risk you’re willing to take with your own health.
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