This three-dimensional sensation is all part of the excitement of diving: being able to move up and down in any direction or being able to just float, in itself is relaxing and a good stress relief. As you gain more experience through further training and diving, you will find it much easier to redistribute your weight to achieve optimum buoyancy and trim. Use the following guidelines to control your buoyancy.
Use lead weight to compensate for the effects of the exposure protection worn in water. The thicker the wetsuit, the greater the positive buoyancy. While swimming underwater, you can displace more water or less water by inflating or deflating the air in your BCD. When using open circuit scuba, the diver’s lung volume will affect buoyancy. This allows you to achieve positive buoyancy at the surface and neutral buoyancy while underwater.
To correctly weight yourself, you need to adjust your weights before you go for a dive; any time you change part of the equipment you dive with, especially thermal protection; and when you move between freshwater and saltwater dive sites.
- Generally, adjust the weights that you carry so that with an empty BCD and your equipment, you float with the top of your head breaking surface, while holding a full breath of air.
- Make sure your cylinders have only 30 bar/500 psi of pressure when adjusting your weight. This simulates a near-empty cylinder much like at the end of a dive. This is important because your cylinder has less negative buoyancy at the end of the dive because the air has been used, so you need to adjust weight for this scenario. Otherwise, you will float to the surface while trying to execute a safety stop at the end of the dive.
- When you have established the correct weighting, simply dump the air from the BCD, and breathe out through your open circuit regulator.
Spend some time finding your correct weighting, and the rewards will be noticeable. Overweighting yourself can be dangerous and make it hard to control your buoyancy correctly. Additional diving training programs build on this skill by fine-tuning your buoyancy.
Moving From One Water Environment to Another
Buoyancy will be affected by diving in salt or fresh water because they have a different density and, thus, different buoyancy characteristics. The Dead Sea (salt water) is so dense that people can float easily without needing to swim, while fresh water is less dense and to stay afloat you need to swim. Sea water is heavier than fresh water by 2.5% to 3% because of the greater amount of salts dissolved in it.
- When moving from fresh water to salt water, a diver has to ADD weight. The amount is not a precise calculation because it depends on factors other than just the buoyancy effects of salt water.
- REDUCE weight when moving from salt to fresh water. Fresh water is less dense and, therefore, has less upward force and less buoyancy, resulting in less weight to be carried by the diver.
- The one factor which is difficult to judge is lung capacity due to the anxiety a diver may have going into a new environment for the first time.
- It is recommended to complete a buoyancy check before diving in a new environment. Don’t waste a dive because you didn’t sort out your weighting!