Most things that you throw into the water either float or sink to the bottom. The former have a positive, and the latter negative buoyancy, but there is also the third group. These have neutral buoyancy, and neither do they sink, nor rise to the surface, but remain at a certain depth. Divers need all three forms of buoyancy, and the effective solution for that is a combination of weights and buoyancy compensator.
What should a buoyancy compensator have?
All modern compensators have essentially the same task, but nevertheless come in different shapes and sizes. The biggest difference is between the compensators for sports and for technical diving. The former look like waistcoats, and the letter have an inflatable compartment only on the back, which is why we call them “wing” compensators.
Sports compensators have shoulder straps, whose length can be adjusted. On the left shoulder is the inflator hose, which is used to inflate the compensator with the air from the tank or with your breath. The compensator also has several venting valves that you can open yourself or they open automatically when the air pressure in the compensator is too high. An important part is pockets and links, on which you can attach various equipment (diving lamp, camera, bows and rope and the like), manometer and octopus. Contemporary compensators, besides ordinary ones, also feature special pockets for weights, so you no longer need a belt with weights. On the back of the compensator there is a plastic plate, on which you attach a diving bottle by using straps.
It is extremely important to choose the compensator, which must be the suitable size, volume and shape (male or female model). Only then will you be able to enjoy your diving experience and to be kept efficiently on the surface (when it is properly inflated).
Up, down, up, down …
Except at the beginning and at the end of a dive, all divers seek neutral buoyancy, in which they consume the smallest amount of energy and air. Neutral buoyancy for some of the less experienced divers at the start is a real puzzle, because they have to consider water pressure, depth, inflating and discharging the compensator and breathing. You can often recognize them by their “yo-yo diving”, because they tend to go up a bit, and they drop down, and then they rise again and drop again.
As a guarantee of neutral buoyancy, it is very important to understand how depth and pressure affect the volume of air. When descending into depth due to water pressure increase, the air volume decreases, while during surfacing the water pressure drops, therefore the volume increases again. Smaller volume means less thrust and therefore lower (or even negative) buoyancy, and greater volume means greater thrust and greater (positive) buoyancy.
Using a buoyancy compensator during diving
In diving, water pressure reduces the volume of air in the neoprene suit, in the lungs of the diver and in the compensator. Normal breathing does not have a major impact on buoyancy, and therefore, the main role is the one of a buoyancy compensator.
At the start of each dive, the compensator must be inflated just enough to keep you on the surface without having to swim. With the release of air, the descent to the depth begins. At the beginning, you can discharge it faster, but when you dive a few meters, stop and start controlling the lowering speed. If it goes too slowly, release some more air, but not too much, as you do not wish to sink too deep or like a stone.
Start inflating some air into the compensator just a few meters above the desired depth, slow down and ensure neutral buoyancy. Adjust and, if necessary, tighten the compensator strap around the body and adjust the shoulder straps, then start swimming at the selected depth. If you are at the beginning of your diving career, you need to have an inflator hose all the time of diving in your hand, so that you can quickly react in case of rising or descending.
Remember that in the depths, due to higher pressure in your surroundings, nothing can happen quickly or immediately. When, for example, you feel that you are descending, do not press the inflator button in panic until the compensator is fully inflated. Press it only for a second or two and then wait for the effect of a larger volume of the compensator. If it is not enough, add more air to the compensator, until the descent stops. It’s the same with rising to the surface, as you have to discharge the air bit by bit, or otherwise you will begin to sink quickly with the discharged compensator. Let’s repeat – carefully monitor your position in the water, and react to the changes calmly and give the air a little more time.
After diving – washing
After each dive, the compensator must be rinsed well with fresh water and then left in the shade to dry. Due to inflating and discharging, seawater can also enter the inside of the compensator, so it must be filled with fresh water through inflation hose several times with to rinse the interior. When you leave it to dry, inflate it slightly and do not leave it in the sun when completely deflated, because the interior could stick together due to the heat.
Text: Matej Ogorevc