In a way, diving can be compared to flying an airplane; the hardest part is taking off and landing. This is true for diving as well; the ascents and descents are often what cause people the most trouble. Once you’re at depth and neutrally buoyant, it’s “easy peasy.” It’s getting to that point and making a nice controlled ascent to your safety stop and the surface that can be a bit tricky…
Making a controlled ascent and descent can add to your overall enjoyment of the dive as well as help prevent barotraumas (pressure related injury). After a controlled descent you arrive at depth already neutral, calm, relaxed, and ready to enjoy the dive. This a vastly different than the over weighted negative free fall many divers make; struggling to equalize and landing on the bottom causing damage to the reef or wreck and ruining the visibility. This is a bad way to start a dive, and it takes time to regain control and enjoy the remaining portion of the dive. Also, this is often the cause of many pressure related injuries to the ears and sinuses because the diver is descending faster than they can equalize those air spaces.
Making a controlled ascent is important for similar reasons. Making a nice controlled ascent to your safety stop, you arrive neutrally buoyant and can hover effortlessly while continuing to enjoy the marine environment around you. You also avoid injury by allowing time for the expanding gas in your air spaces to escape safely. All too often we see divers “float” up and blow right past their safety stop ending up at the surface wondering what the heck happened. We are going to take a look at how to control your ascent and descent by using the art of buoyancy control.
In order to control your descent, you should remain neutrally buoyant. This seems counterintuitive at first. “If I’m neutral, how am I going to go down?” Well, if you are properly weighted you should really only be descending when you exhale all the gas out of your lungs, and you should only be descending a couple of feet at a time. We were all taught in our open water course, that to be properly weighted and an empty BCD you should float at eye level while holding a full breath. When you exhale, you should become slightly negative and descend, when you take another breath, you should become neutral again. As you descend in this controlled manner, you will need to add small amounts of air to your BCD every few feet to counter the compression of your wetsuit/dry-suit and BCD to remain neutral. This allows you to easily stop your descent to equalize, acclimate to a thermo-cline, make contact with your buddy, watch that dolphin swimming by, or avoid landing on the bottom. Now you will arrive at your target depth already neutrally buoyant, air spaces comfortably equalized, and ready to look for that dolphin you spotted on your way down!
Ascending should be pretty much the same process, just in reverse. You should already be neutrally buoyant, so to ascend you should only need to swim lightly towards the surface. Now it’s extremely important to monitor your dive computer’s ascent rate indicator to make sure you are going up at a safe rate and vent the expanding gas out of your BCD so you do not become positively buoyant. If you become positive, you can find yourself on an uncontrolled ascent to the surface. Floating up, the air in your BCD can begin to expand faster than you can dump it, which makes you even more buoyant and you float up faster while the air in your BCD expands even faster. This is a dangerous situation which can result in a barotraumas or even decompression sickness. To avoid this potentially hazardous situation, pause every few feet on your way up to make sure you are not starting to float towards the surface. This way, once you reach your safety stop, you can easily just hold your position hovering weightlessly showing off your excellent buoyancy skills to that dolphin that decided to come back to play.
Your safety stop is an excellent place to make a final weight check. If you are weighted properly, you should have almost NO air in your BCD at the end of the dive and be perfectly neutral. If you are struggling to stay down, you may need another pound or 2, if you have to add air to your BCD to remain neutral, you can probably take a little weight off for the next dive.
Like everything else, practice makes better. Luckily, on every dive, you have to make at least one descent and ascent, so you may as well use this time to practice. We’ve found that using a line or sloping bottom as a visual reference is a great way to get your ascents and descents dialed in, and suggest using them to hone your skills whenever available. Even better than practicing on your own, is having an instructor help you through it with an SDI Advanced Buoyancy course. Find an instructor near you here!
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