How’s your Buoyancy?
Probably the first experience of buoyancy control for most of us came in the swimming pool. During pool swimming sessions, you became to realise that a deep breath-hold would keep you afloat. When you exhaled deeply, you found you would sink. This is still the basics of scuba diving buoyancy control today.
In our Open Water Course, you learnt buoyancy control. You learnt to hover using your low-pressure inflator, and by means of orally inflating your BCD. If you breathe in you will rise and if you exhale you will start to sink. Fin pivot is a typical exercise in the open water course in which you practice the rising and sinking by inhaling and exhaling. You became to understand that if you moved around too much, with your arms and legs it would send you off balance and in a different direction.
What is neutral buoyancy?
Neutral buoyancy is a weightless state between the surface and bottom. The depth of neutral buoyancy will be determined by the diver by adding air to the BCD. Student divers learn that increased neoprene and dive gear will change their natural buoyancy. To achieve the neutral buoyancy state, weight must be added to compensate for the positive buoyancy of the neoprene suit. Being able to control your buoyancy is one of the most important skills you will learn when learning to scuba dive.
Safety and Air consumption.
Correct buoyancy will improve your safety, improve air consumption, and reduce fatigue. Not only does it enhance the enjoyment of the dive, but it helps to protect the underwater environment from damage caused by fins, hands and dangling equipment. Most human beings in their swimsuit or ‘birthday suits’ are neutrally buoyant. However, the generous fat layers on some human beings cause them to be positively buoyant and they will float. Muscular and lean bodies are opposite, they are negatively buoyant and will sink.
Diving incident reports.
Poor buoyancy control and overweighted divers are cited as a contributory factor of diving accidents, or near accidents. A study carried out in New Zealand covering 100 scuba diving fatalities showed 45 per cent of the victims were believed to have been overweight, with 40 per cent being at least 2 kilograms negatively buoyant at the surface. In Australia, another study included 533 diver incidents with 57 reported cases of malfunctions with their BCD’s. Of these 57 incidents, 21 of them involves rapid ascents with harmful consequences.
Weight belts and weight problems made up 27 cases of the 533 diver incidents. These two pieces of equipment must be thoroughly understood, and their function should be very clear. The report of cases with BCD malfunctions was mostly due to an error of the diver. The case reveals many divers (especially newly certified divers) do not fully understand the full function of a BCD. Weights and weight belts are vital to buoyancy control, but overweighting should not happen.
Practice makes perfect.
Buoyancy control is said to be very important, however many Instructors do not devote enough time for practice. The basic Open Water Course is there to practice skills such as buoyancy, weight distribution (trim) and neutral buoyancy. Correct weighting is paramount in the OWD course, and a weight check should be done regularly as they progress through the course. Most divers who complete an OWD course leave their course overweighted. This is a cause for concern as the newly certified diver is led to believe that he or she carries the correct amount of weight. It is a substantial risk to novice divers if they are not taught with the correct amount of weights. Do not just put weights on students to keep them down, check and reduce as necessary.
How to do a weight check.
When you try to achieve neutral buoyancy at the surface, weight yourself so you are suspended vertically in the water. The top of your head will just touch the surface with a fully deflated BCD when you hold a normal breath. Inhale deeply and you will rise, exhale you should sink. This exercise is best carried out with 50 bar cylinder pressure at the end of a dive. It is very important that all divers have enough weight to be neutrally buoyant at 5 meters on the safety stop. It is not acceptable to shoot from 5 meters, after completing the safety stop straight to the surface. Remember, the Nitrogen bubbles expand quickly even in shallow depths.
Neoprene wetsuits vary in thickness. If you change your wetsuit thickness, you must do a weight check. If you used an aluminium cylinder, then change to a steel cylinder, a weight check is necessary.
During the descent, it is important we add small amounts of air to our BCD. A deeper dive requires buoyancy control to slow the descent rate. This enables the diver to quickly trim off into neutral buoyancy on arrival at the desired depth. If you don’t add air to the BCD on the descent, it will be very difficult to come back to the surface. Your ascend will be very difficult and require a lot of energy and air if you have a completely deflated BCD at depth. The amount of air you use will rise considerably due to the effort required, in order to reach the surface.
How much BCD lift do you require?
The fit of the BCD is essential. It must have sufficient lift to allow the diver to maintain neutral buoyancy at depth. A BCD which is too small might not support the diver at depth. This leaves the diver must exert themselves to maintain neutral buoyancy. This will lead to an increase in air consumption and a higher risk of decompression illness. A BCD which is too large, when inflated at depth it will ride up the divers back. It will not stay in the correct position and will move around the diver’s torso. The BCD becomes difficult to deflate on the ascent and can lead to excessive ascent rates.
Neutral Buoyancy is paramount to being a good, safe diver. It is a must to help take care of the environment. If you have buoyancy problems, come and do a PADI Peak Performance Buoyancy course with us at Dive Smart Gozo. This course will help you in many ways to become a good diver, and it is great fun.