The Importance of Buoyancy Control

Controlling buoyancy is a key component of your diving safety. The physics of floating and sinking are simple concepts, yet achieving practical control of your buoyancy when outfitted with scuba equipment and immersed in water is an entirely other matter. Each change in equipment affects your buoyancy. As your dive equipment grows more complex, the more attention your buoyancy requires. Given its role as a fundamental element of dive safety, it’s no wonder problems with buoyancy control are often the underlying cause of a dive injury or fatality.

Divers with proper buoyancy control can maintain their position with very little effort. They can descend or ascend at will. In contrast, divers with poor buoyancy-control skills struggle throughout the dive. In extreme situations, major buoyancy-control issues may cause divers to make grave errors such as descending well beyond their planned depth, negatively affecting gas consumption and no-decompression calculations, or on the flip side, uncontrolled ascents, increasing the risk of decompression illness.

There is no doubt buoyancy control affects many aspects of dive safety. Experts in dive training, dive medicine and research all know just how integral it is and are always eager to share thoughts on how to develop and maintain good skills.


Female diver in crossed-legged position overs in water

Good buoyancy begins with proper weighting. It is imperative the amount of weight you use allows you to descend, not causes you to do so. Weight placement makes a difference, too. A classic buoyancy-control device (BCD) is generally configured to require a separate weight belt, whereas newer BCDs often integrate the weights. Each approach affects a diver’s body position in the water, requiring time and attention to get comfortable. Using rental gear can complicate the process, especially for new divers, as each change in configuration, responsiveness and other variables can alter a diver’s comfort and buoyancy. Diving with a drysuit, a weight harness or a rebreather adds to the complexity.

The BCD is the most complex piece of scuba equipment a diver must master. To truly master buoyancy control, a diver must understand his BCD inside and out, including knowing how it reacts to the addition or venting of air. It requires proper maintenance (see “Gear,” Alert Diver, Spring 2011) to prevent sticking buttons or leaking bladders. Malfunctioning BCDs can lead to uncontrolled ascents or descents before a diver even realizes what’s happening. Like any piece of equipment, proper function requires proper maintenance.

But lack of maintenance is not the only concern; operator error can also cause loss of control. Improperly connecting a low pressure inflator can cause negative buoyancy without a means to correct it. Hitting the inflator button instead of the vent button can cause a rapid ascent. Every diver needs to be familiar with his own equipment as well as his buddy’s. In a stressful or emergency situation there may not be time to search for weight releases or inflator/deflator valves.

Dive Medicine

Many do not equate buoyancy skills with dive medicine, but there is definitely a connection. The most common dive injury is consistently middle-ear barotrauma. There are certainly many factors that lead to this injury, but buoyancy issues are often among them. Every diver is taught that if discomfort is felt during descent to stop the descent, ascend a few feet or until the discomfort resolves, and then attempt to equalize again. This is very difficult to execute without good buoyancy control. When experiencing a reverse block during ascent, a diver should stop the ascent, descend until the discomfort resolves and attempt ascent again using appropriate equalization maneuvers. The ability to stabilize and adjust position in the water column certainly takes practice, but as a cornerstone skill, it’s worth the effort.

Most marine life injuries are due to incidental contact. Proper buoyancy helps divers avoid contact as it maintains necessary distance from marine life. It also prevents the destruction of the reef and the microscopic critters that live on subaquatic surfaces, as buoyancy control reduces the need to place hands on those surfaces to steady a diver’s position. Buoyancy skills not only protect divers but the environment as well.

Finally, one of the most serious consequences of inadequate buoyancy control is a rapid ascent. This can place a diver at risk for a lung overexpansion injury (pulmonary barotrauma), and it also increases the risk of a potentially fatal arterial gas embolism (AGE). The easiest way to avoid both these injuries is to learn the best method of prevention: good buoyancy control.


When reviewing dive accident reports, DAN® researchers look for triggers and contributing factors. In cases where buoyancy problems are reported, the most frequent trigger was running out of air, and a rapid ascent the most frequent cause of injury. Running out of air and rapid ascents may be obvious causes of fatalities, but our analysis reveals that buoyancy problems, a less-obvious factor, precede them in many cases.

Exceeding planned depths increases decompression stress and creates a situation where divers consume gas supply more quickly than planned. Being low on or out of air is the most often reported trigger; this in turn prompts a rapid ascent. Adequate buoyancy is an essential element in proper gas management, and controlling depth is only one part of this. Fewer adjustments to buoyancy reduces air consumption, as does the reduced effort that comes from the ability to maintain a streamlined, hydrodynamic attitude. Any reduction in effort at depth can reduce decompression stress; good buoyancy goes a long way to helping achieve that goal.

Another danger in reaching an unexpected deeper depth is nitrogen narcosis. Its intoxicating effect can impair judgment, performance and reasoning. It can also create a sense of euphoria and, in some cases, fear. The potential for danger when encountering nitrogen narcosis unexpectedly is clear, as are the steps that can be taken to avoid it.

Keep It Going

The mastery and maintenance of buoyancy control is a journey that never ends. It will become second nature after a while, but it’s important to remember how any changes to your gear configuration can affect buoyancy and create struggles that are easily avoided with a little time and attention. Work through buoyancy issues before they become problems, emergencies or fatalities. Take advantage of workshops and buoyancy clinics offered by dive professionals, and seek refresher training if you have been away from diving for extended periods. These are investments well worth the time and money.

© Alert Diver — Q4 Fall 2011