• A diver should be able to control his buoyancy well enough to stop at any moment of the descent and quickly achieve neutral buoyancy.This type of descent is a required skill in PADI Open Water Course (called a controlled descent without a reference).
• A diver should also be able to complete the descent without touching the bottom.
Why Learn to Control Your Descent?:
The ability to make a controlled descent is important for three reasons:
1. If a diver experiences ear equalization problems and he cannot arrest his descent, he risks an ear barotrauma.
2. A diver must be able to descend without landing on the bottom because even a gentle fin kick can irrevocably injure coral or other aquatic life. Landing on a shipwreck or cave floor can not only destroy delicate historical information, it can stir up sediment to the point that visibility is dangerously reduced.
3. A diver should be able to stay close to his buddy during descent. A diver who plummets to the bottom will be unable to assist a buddy making a slower descent.
Step 1: Understand the Use of the BCD:
Step 2: DO NOT Dump All the Air From the BCD to Begin the Descent:
Step 3: Exhale Fully to Begin Your Descent:
Once you are neutrally buoyant at the surface, begin your descent by exhaling fully. This takes some practice as you must exaggerate your breathing. Exhale all the air out of your lungs slowly (with the regulator mouthpiece still in your mouth) and then hold the air out of you lungs for a few seconds. Try this now: exhale, exhale, exhale, exhale more, more, and now hold the air out of your lungs, try to exhale even more. . . good! The exhalation process should take around 10 seconds. Expect to slowly sink near the end of the ten seconds, and be patient. If you find yourself back at the surface when you inhale, deflate the BCD a little more and repeat the process. When performed properly, the exhalation will move you far enough down in the water column that the air in your BCD compresses, and you begin to sink slowly (Confused? Review why water pressure compresses the air in you BCD as you sink.)
Step 4: Reestablish Neutral Buoyancy:
Step 5: Regroup:
Step 6: Descend by Exhaling Once Again:
More scuba diving skills:
Doesn't This Kind of Descent Take Forever?:
As you gain experience with controlling your descent, you will become more efficient and effective. Eventually, you will deflate exactly the correct amount of air from your BCD in one shot, exhale and float down, add air to compensate for the increased negative buoyancy at the correct moment, and continue quickly down.
Once mastered, a controlled descent is more efficient than dumping the all air from your BCD at the beginning of the dive because you do not waste time fighting with your buoyancy on the way down. You arrive at your desired depth neutrally buoyancy and ready to swim off on your adventure. Be patient. Every diver can properly control his descent with understanding and practice.