Underweighting can be just as dangerous as overweighting.

scuba diver in lotus position

Equipment and the Environment Will Both Affect Your Buoyancy

Wetsuits, tanks, and even accessories and tools will affect your buoyancy. Whenever you change one of these items, it is necessary to complete a buoyancy check to determine the effect of the new item on your buoyancy. The salinity of the water will also affect a divers buoyancy. The obvious example is buoyancy in fresh water vs salt water, but keep in mind that the salinity of the ocean may also vary in different regions of the world, and you may need slightly more or less weight depending upon your dive location.

Conducting a weight test before a dive can make the difference between a miserable dive and an enjoyable one.

 

Conduct a Buoyancy Check Before DivingScuba 2

Test your buoyancy in a new location or whenever diving with a new piece of gear. Most of the time, diver’s have a limited number of dives on vacation, and it is worth the effort to make every dive comfortable and safe.

In fact, most dive operators will be thrilled if you ask to wade into the ocean or hop of the pier before your first dive to double check your weighting.

 

The general rule of thumb for proper weighting is that with all of his gear in place, with a nearly empty tank, a diver who completely empties his BCD and holds a normal breath should float at eye level. When he exhales he should sink.

 

Remember!! As the tank empties, it will become positively buoyant.

If you can empty your BCD, hold a normal breath, and float at eye level at the beginning of the dive, you will not have enough weight to comfortably maintain neutral buoyancy at the end of the dive.

The problem here is that most dive shops are not in the practice of providing nearly empty tanks for buoyancy tests. There are two solutions to this:

 

  1. Conduct the buoyancy test with a full tank as outlined above, and then add the appropriate amount of weight to offset the buoyancy swing of your tank as it empties.
  2. Conduct the buoyancy test as outlined above with a full tank, but instead of checking that you float at eye level, check to see that you sink slowly while holding a normal breath.

 

Double Check Your Buoyancy at the End of a Dive

Once you have successfully completed a dive with enough weight to keep you comfortably below water the entire time, it is a good idea to double check your weighting at the end of the dive.

To do this, purge your regulator gently until you are down to about 500 psi or 30 bar. Then, on the surface, conduct a buoyancy check before exiting the water. Do you float at eye level and sink when you exhale?Scuba 3

Do you have to swim to get down? Float like a balloon on the surface? Add a little weight on your next dive.

Do you still sink while holding your breath? Remove a few pounds and try again on the next dive.

 

Adding a Small Amount of Air to Your BCD During Descent Is Good

Many divers seem pleased that they can descend and arrive at the planned depth without adding air to the BCD.

Again, this is not a desirable situation. Because most tanks become more positively buoyant throughout a dive, divers who do not need to add air to their BCDs during descent to establish neutral buoyancy are likely to be underweighted.

 

I Don’t Need to Add Air During Descent. I Am Fine at the End of the Dive!

These are the people who have exceptionally low air consumption rates, and surface with at least half of their air remaining. Yes, they can be perfectly neutral during their safety stops, and they don’t go flying to the surface like awkward buoys at the end of the dive. Their tanks have not become positively buoyant because they haven’t breathed enough gas to cause a buoyancy swing.

 

The problem with this habit is that it does not prepare divers for an emergency situation, when they are low on gas because they over-breathed a tank due to a stressful situation, surface with less gas than normal due to an unforeseen occurrence, or are forced to share air with another diver.

In these situations, such a diver will have trouble staying down, and of course, these are the situations when having enough weight can make a big difference between an annoying situation and an uncontrolled ascent to the surface.

Plan for the worst case scenario: a low tank and increased breathing rates due to stress.

 

Diving with less weight does not make you a better diver.

Diving with the correct amount of weight does.

Slight overweighting is correctable: just add a little air to the BCD.

To be safe on dives, proper weighting is key.

Take the time to get your weighting right and you can avoid many potentially dangerous situations and dive more comfortably.

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Buoyancy Basics – Seven Ideas for Adjusting Trim Without Adding Weight

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Before making any adjustments to his gear, a diver must first check his trim. He should enter the water with all of his diver gear and attempt to hover in a horizontal position without moving his fins or arms. He can then note whether he has a tendency to hover head or feet up, or to roll to one side.

1. Move Weights Around

Changing the position of a diver’s weights may help to adjust his trim. Many buoyancy compensators (BCs) have trim weight pockets just below the diver’s shoulders. A diver who tends to float head-up may use the pockets to redistribute his weights, placing a few pounds in each pocket. For example, a diver who uses ten pounds of weight may want to carry six pounds on his weight belt and four pounds (two on each shoulder) in his trim weight pockets. If a diver’s BC does not have trim weight pockets, some divers will place a weight on the BC’s tank band for a similar effect.

Redistributing weights is not always possible, as in the case of a diver who uses very little or no weight, or a diver who uses a BC without trim weight pockets. Some divers simply find that redistributing weight does not correct their trim. Fortunately, it is possible to manipulate other pieces of dive gear to perfect a diver’s trim.

2. Tank Position

A diver’s tank position affects his trim. A tank can be lowered or raised in relation to a diver’s BC by changing the position of the BC strap on the tank. A diver who attaches his BC strap near the top of his tank will find that the tank sits low on his body. This may help to correct for a foot-up position by shifting the weight of the tank towards the diver’s feet. Attaching the BC to a lower part to the tank will have the opposite effect.

3. Reposition the Buoyancy Cell

Some equipment configurations, such as a backplate/ wing system, allow a diver to move his buoyancy cell (the part that inflates and deflates) upwards or downwards in relation to his harness. A diver can move the buoyancy cell towards his head to compensate for a foot-up position, or towards his lower body to correct a head-up position.

4. Change Your Neoprene

The thickness and distribution of a diver’s neoprene garments can have a huge effect on his trim. Thick, full-length wetsuits, especially wetsuits that have 5 mm or 7 mm legs, have a tendency to cause a diver to float feet-up. Switching to a wetsuit that has a 7 mm torso and thinner legs can remedy this situation. Similarly, thick wetsuit booties can cause a diver’s feet to float. Simply switching to thinner booties may solve a foot-up position. Finally, warm-water divers who find themselves floating foot-up may consider switching to a short wetsuit, as long as the suit still provides adequate thermal protection.

Adding neoprene layers to the torso may also have a slight effect on a diver’s trim. Thick vests and hoods add buoyancy to a diver’s upper body, and may be useful in compensating for a foot-up position.

5. Change Your Fins

Changing your fins may sound like a drastic step, but switching your fins can often be a helpful method of correcting trim. Different brands and styles of fins have astonishingly different buoyancy characteristics. For instance, SCUBAPRO Jet Fins are some on of the most negatively buoyant fins on the market. Other fins may be neutral or even positively buoyant. Heavier fins can compensate for a foot-up position, while lighter fins can compensate for a head-up position.

6. Change Your Regulator First Stages

Regulator first stages can be very heavy or relatively light. A heavy regulator first stage can help to fix a head-up position, and a lighter regulator first stage can help to compensate for a foot up-position. Of course, regulators should be selected first and foremost for their breathing characteristics, but given the choice between several similar first stages, a diver may want to make his final decision based on weight. The weight of the first stages is of particular interest to technical divers, who use at least two first stages on every dive.

7. Consider Your Accessories

Finally, a diver may want to take a look at his accessories and consider their effect on his trim. A diver who carries a heavy dive light may have a tendency to list to one side — in this case he may want to place other accessories (or counterweight in a worst-case scenario) on the side opposite side of his light. Divers who carry huge, heavy reels on their rear d-rings may notice that they float head-up. Switching to a lighter reel may fix this problem without any other adjustments.

In most cases, a diver’s trim can be adjusted without adding weight. Before making any adjustments, a diver should attempt to hover in horizontal trim with all of his dive gear in place (even accessories) to diagnose any trim problems. He can then begin repositioning or changing dive gear to improve his trim. It is advisable to change or reposition only one piece of gear at a time, and to get into the water after each adjustment to evaluate its effect. It is difficult to determine the result of an individual alteration when several adjustments are made at once.

 Take your time and make methodical adjustments to your equipment, one change at a time, until you are happy with your trim.

Controlled Descent

Descending from the surface should be as easy , but it sometimes can deteriorate into an exhausting struggle with our gear and our mounting anxiety.

The solution is to handle descents the same way you’d eat an elephant: one bite at a time.

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.

Avoid task-loading problems by breaking down your descent into discreet, manageable steps

On the Surface

After you and your buddy make your entries, don’t rush to descend. Relax, regroup and recheck. Make contact with your buddy, clear the entry area and float comfortably buoyant with your snorkel or regulator in your mouth and your face in the water.
Take a few moments to establish a slow, full breathing pattern and acclimate to the water temperature, especially if it’s cold. Then begin to methodically recheck your gear to make sure nothing has come loose on entry — your weight belt buckle or your mask strap, for instance. Listen and look for hose leaks and freeflows. If you’re wearing a dive computer, confirm that it is activated. Once you’re satisfied that everything is in order, visually check over your buddy’s equipment.
If surface conditions such as a current or wind chop make you uncomfortable, these checks can be performed while holding onto a current line or just under the surface on a descent line.
Practice your ear equalization technique a couple of times to loosen up the muscles. As a last step before descending, compare gauges and set your watches.
Begin Your Descent
Once the “thumbs down” signal is given, both buddies should begin their descent at the same time and remain together all the way to dive depth. Keep your right hand free to equalize your ears as you drop below the surface.
To start your descent, establish negative buoyancy by venting air from your buoyancy compensator (BC).

With your left hand, raise your deflator hose straight above your head and depress the button while dipping your right shoulder. This position will ensure that the air has an unobstructed path to flow up and out. If you have previously performed a weighting check and are correctly weighted, you should immediately begin to descend slowly and effortlessly.
If you fail to sink, first stop all kicking and other body motions and exhale fully. This is often enough to trigger a normal descent. Next, try squeezing any remaining air out of your BC while keeping the deflator hose up and the button fully depressed. Only after you’ve tried the above should you consider adding weight.
Some divers try to deal with an inability to sink by “duck diving” — swimming head down to propel oneself under the surface. This takes a lot of effort and also makes equalizing difficult. A better option is to use a descent or down line, which often hangs vertically into the water near the entry area of the boat especially for that purpose. Or you can use the boat’s mooring or anchor line.
Try easing yourself down the first few feet (1 m) along the line while remaining in an upright position; remember to equalize your ears as you go. You may be properly weighted but just need that little bit of increased pressure to force out air trapped in loose spots between your body and wet suit and in your gear. It is also easier to relax and exhale fully once your head is under the surface. If you still don’t sink, you’re probably underweighted.
If you determine that you are either under- or overweighted enough that you can’t proceed with a safe, enjoyable dive, signal your buddy to abort the descent. Return to the boat to add or subtract lead.
To control anxiety, stop your descent and hold onto the line until your breathing and heart rate return to normal. Remind yourself to clear your ears often by equalizing every time you move your hand down on the line.

Allow yourself to float downwards until you can no longer easily control your buoyancy with your lungs. Once you reach the point that you continue to sink when you inhale, you are no longer neutrally buoyant. When you are neutrally buoyant you should rise slightly when you inhale fully. Remember, the goal is to maintain neutral buoyancy throughout the descent, not negative buoyancy. Add a tiny, tiny amount of air to your BCD. You should be able to stop descending or rise slightly when you inhale. Take some time to find this point of neutral buoyancy.
Regroup:
After descending a few feet and reestablishing neutral buoyancy, take a moment to check that your ears are properly equalized. Look at your depth gauge and notice if you are approaching or have reached your intended depth. Check on your buddy. If all is good . . .

Descend by Exhaling Once Again:
Once you have regrouped, continue your descent by exhaling fully. The goal is to control your descent by working your way slowly and carefully down through the water column using you lungs to descend and your BCD to keep yourself neutrally buoyant. When you arrive at your desired depth, you should have to do very little to fine-tune your buoyancy.

Equalize, Equalize, Equalize
As soon as your head sinks below the surface, equalize your ears and continue to equalize at least every couple of feet all the way to dive depth . The key to successful ear clearing is “early and often” — start early and do it often. This prevents pressure from building up against the eardrum, causing pain and difficulty equalizing.
Don’t continue your descent if you do experience ear discomfort; it won’t get better. Instead, ascend a few feet until you can equalize, then continue your descent more slowly, equalizing even more frequently . You can’t equalize too often.
Avoid looking down while trying to equalize; it can pinch the Eustachian tubes, making them more difficult to open. Raise your chin and stretch your neck to each side to help air flow through the tubes. Blowing harder is not the answer.

Slow Your Descent
The deeper you descend, the more negatively buoyant you’ll become as the increased pressure compresses the air spaces in your exposure protection. You may need to slow your descent by adding air to your BC with short bursts from your power inflator .
Stop your descent at least 1 m before you reach dive depth. Make yourself neutrally buoyant and hover. Confirm with your buddy that you’ve both completed a successful descent. Roll to a horizontal trim and begin your dive.

By taking it one bite at a time, every descent will start you off relaxed and ready to enjoy a perfect dive.

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.