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SCUBA DIVING SAFETY
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Buoyancy Control - The Keystone of Good Diving
I have long taught my students that there are two things that
separate good
divers for the pack. That is
buoyancy control and dive planning.
And there is
more to both of them than you think. Read on and then gather up
your gear and
go out and practice because if the last time you practiced buoyancy control
was during your basic course, I can assure you that your buoyancy control
leaves a lot to be desired.
Three Buoyancy Compensators (BC's)
to better buoyancy control.
That's right, three bcs. First of all, there is your buoyancy
compensator,
which is what most people think about when we talk buoyancy.
But there are
two other bcs, Breath Control and Body Control. Let's take
them in that order.
Your Buoyancy Compensator
The buoyancy compensator is used for gross changes in buoyancy. These changes
take place due to wet suit compression, compression of air in our bc, and
changes in the weight of our tank as we use up our air. There are a few
things that are important to remember about our bc. First of all it is not an
elevator,! We do not use our bc to bring us to the surface and allow us to
sink. We use our bc to maintain neutral buoyancy at all times. This is a very
important concept. Let's look at the proper use of a bc during a dive.
You add a little air to your bc prior to entering the water. This assures
that after hitting the water, you return to the surface immediately. This
allows you to make sure your mask strap is still in place, your weight belt
is not sliding down, and you are with your buddy. It also allows you to
signal the boat crew that you are ok. (Admittedly, some very experienced
divers enter the water with no air in their bc and commence their descent
immediately. But these are very experienced divers.) To start your descent,
you should let all the air out of your bc and then using either a line or a
surface dive, begin your dive. I prefer to swim downward on a slight angle,
clearing my ears as I go. Remember, if you are descending feet first, the
greatest drag created is by your fins. This will usually cause you to lean
backwards and you will find yourself descending butt first! At this point you
are actually falling through the water. If you can not clear your ears, it is
difficult to stop your descent immediately. If you are swimming down, all you
need to do is level off to stop the descent. Now, as you continue your
descent, you need to add air to your bc to maintain neutral buoyancy or at
least be close to neutral. Do not wait until you reach the bottom to start
adding air. If you do that, then you need to add a lot of air to get it
right. If you make big changes, then you can make big mistakes. Make small
changes and you will only make small errors that are easier to correct.
Throughout your dive you will need to make changes as you change depths or as
your tank gets lighter due to air consumption.
At the end of the dive, as you start your ascent, you must start letting some
air out of your bc in order to maintain neutral buoyancy during the ascent.
If you do not, the air in your bc will start to expand, your wetsuit will
start to recover from its compression, and you will start to be carried to
the surface by your buoyancy. This is not buoyancy control. If all of a
sudden a boat motor starts or a boat starts to approach the area, you can not
stop your ascent easily. If you were neutrally buoyant, you would stop where
you stopped kicking. That is a controlled ascent.
It is also important that you know your bc. If you want to learn more about
bcs, look at our equipment section for the piece I wrote on bcs.
The bottom line is: you let all your air out to start your descent, then you
add air as your descent continues. As you ascend you let air out until you
reach the surface, then you add air to keep you afloat at the surface. Got
that?
Our second "BC" is body control. Understand that your body wants to go in the
direction that the top of your head is pointed. If your point your head up,
your body goes up, if you point your head down, your body goes down. That
said, let's explore body control.
Newton's Second Law states that "For every reaction, there is a direct and
opposite reaction." First of all note that Newton said for "every" action.
That means if you are at the surface and have let the air out of your bc and
you expect to sink, that the best way to do that is not feet first. That is
because every move you make tends to push you back to the surface. If you
just move your legs to balance yourself, that action has an opposite reaction
(pushing you up). If you move your hands through the water, there is an
opposite reaction to that action. Your best bet is to do a surface dive and
then the movement of your fins pushes you downward.
Remember as a kid, holding your hand out the car window to ride the air
waves". Tilt your hand up and it goes up, tilt your hand down and it goes
down. Your body acts like that in the water. If your are swimming along and
you tilt your head up, your body goes up. Therefore your body must be
parallel to a depth if you expect to remain at that depth. The problem comes
in the way we where our equipment. If we are wearing our weight belt around
our waist, it is really in the wrong place. We should be wearing it around
the center of buoyancy. For most of us that is probably 8 - 10 inches above
our waist. Of course, it is not practical to wear a weight belt there so we
wear it lower. But that pulls our legs down, which means our head is pointed
upward and we go up. How do we deal with that? We add more weight! And our
legs sink even more. We made the problem worse. This circle continues until
we have add so much weight that no matter where our head is pointed, we are
not going up! And now when we get to the bottom we need to add that much more
air to our bc to compensate for this excess weight. Of course, that air goes
around the top half of our body and compounds the problem. Our body control
is not under control. At this point we are now pushing our body through the
water on an angle and not in a streamlined head-first position and we are
pushing our bc through the water half full of air. Try pushing an empty bc
through the water and try pushing a bc full of air through the water and see
the difference. So the amount of weight that you use corresponds to your body
position as you push it through the water.
Notice the way a shark swims as it moves through the water. It is propelled
by its tail (as we are propelled by our fins). When he wants to turn, he
draws in a pectoral inward tilting his body in the direction of the turn. He
then arches his back and glides through the turn. You can do the same thing.
You want to turn? Drop one shoulder, arch your back, continue to kick and
watch your body go through the turn. Your hands never leave your side. It is
like flying. Practice it and you will be amazed at how effortless it is.
We all know that every time we inhale we go up and every time we exhale we go
down. So it must have some effect on our buoyancy. It definitely does. We can
use that effect to our advantage.
When someone realizes that they are too buoyant, the first thing they do is
reach for their inflator hose and bring it up above their head to dump air.
Two other things happen at the same time. By going into a head-up position,
they proceed to move even shallower and, secondly, they are now pointed in a
position to move them even shallower yet. What they should have done is
quickly exhale and held that breath out. Yes, I did say hold your breath, but
I said hold it "out." By exhaling you quickly get rid of several pounds of
buoyancy. That buys you little time to get a hold of you inflator hose and
dump some air. Remember, you don't need to dump it all, just a little. You
should just be a little off. Also, make sure that you use the rapid exhaust
at the top of your inflator hose or the dump on the back of your bc to do
this. If you are not sure how these work, talk to one of our staff and they
will demonstrate it for you.
So, you can see that you can use breath control to your advantage.
The bottom line is that proper buoyancy control takes all three of these
methods. And proper buoyancy control is not something that just happens. If
you think that someday it will just come to you, look in your Day-timer.
Someday is not there. But if you practice these techniques, take an advanced
course, think about how your movements and prescence in the water translates,
and you work on buoyancy for the next 25 dives that you do, you will never
have to think about it again. And you will be part of that group of divers
that every one admires because you make it look so easy. Go for it.
You -- Your Knowledge and Your Physical Condition
Your Equipment
Where Are We Going?
The Day Before
The Dive - Finally
The Missing Link
See, you have to read on to what the missing link is. Well, it is the one action that nobody takes in dive planning - the debriefing.
If you don't talk about what happened you will see the same problems come back to haunt you again and again. Discuss those
problems even if they are minor. it will prevent them from growing.
As you can see, the bottom line is that if you only spend a few minutes planning a dive, you are compromising the safety, fun
and comaraderie of diving. So get your diving planning act together.
Dive Planning - It Separates the Pros and the Amateurs
I have long said that there are two areas where most divers don't pay enough attention -- Buoyancy control (see above) and
dive planning. Most people look will tell you that they do plan their dive, but as you can see below, there is a lot more to it.
You first started dive planning when you decided to get certified and made the calls to find out what steps were necessary to
achieve that goal. In doing so you had made a critical evaluation - that you did not have the skills and the knowledge to
be a diver. You made plans to change that. You need to continue to make that evaluation over and over again as your diving
career progresses. You also need to make a few other evaluations relating to your physical condition and your equipment and your
choice of dive locations.
This is the tough one. Look in the mirror - you handsome devil (or devilette). You want to think that you are in as good as
shape as ever and can still do all the things you used to do. I always say "I can still do all the things that I used to do,
but it hurts a lot more (and a lot longer.)" The truth is that most of us are not in the same shape as we were a few years
ago. (I know there are a few exceptions and I don't really hate you.) Age and job stress do take a toll, sometimes subtly. You
need to be hard in your evaluation of your physical condition. Is it time to get to the gym or back on the bicycle? Do you need
to lose 10 pounds (if just to get back into your wetsuit)? Are you still smoking (you know it is killing you.)? What are you
going to do to change these things. If nothing, then maybe you need to change the type of dives you are exposing yourself to.
Unfortunately in diving today there are a number of fatalities caused by heart failure. In a sport only 50 years old, we are
seeing a population that is aging. That needs to be considered in our evaluation of ourselves.
The other side of looking at ourselves is "What are our skills like?" Is this the year that we take the Advanced course, or the
Rescue course, or maybe Nitrox or Equipment Specialist? Are you planning on becoming a Scuba Instructor someday and want to
get moving on that path. If there is something you plan on doing "someday", look in your day planner. You will notice "someday"
is not in there. Maybe there will be one in your next life. Or just maybe you should sign up for that class NOW. Make a plan.
Now that you understand this part, let me say that you need to do it every year. I tell my students to look at it at the beginning
of the year, make these evaluations and get it on their calender. You can click here to look at our course
schedules and descriptions. Find out when the course is given and block off those dates.
If you are a certified diver, you have probably have already figured out that diving is an equipment-intensive sport. Having
the proper equipment (properly maintained) is very important. Remember that this is life support equipment. Again, from the perspective
of the beginning of the year, we need to make some evaluations about our equipment and make some plans relating to it. First of
all, do we have our own equipment. If you do not it will be hard to ever become a really good diver. If you tried to play
tennis with a different tennis racket every time or golf with a different set of golf clubs each time, you would never get any good at it.
Diving is the same. If you do not have your own equipment, read our piece on "How to Buy You Own Dive Equipment".
If you do have your own equipment, you need to decide if it is still sufficient for the diving that you are planning on their boat.
doing. Does it need to be replaced, serviced, or modified. We have several upgrade programs available. Give us a call. If your equipment
needs to be serviced, you need to get it to us in January or February. If you wait until April, (like all those other people who do not
do any dive planning), then we are swamped with equipment that needs to be overhauled. Get it to us early. Get in the habit of bring it in
January and it will be due for it's next overhaul in January. Then we are not rushed trying to get it done in time for you.
If you are planning on renting equipment, you don't need to do it in January, but you do need to do it in advance of when you will
need it. In advance does NOT mean two days in advance. It means more like ten days in advance. You might get away with two days, but don't
count on it. Sooner or later your luck will run out.
Now that we know that we and our equipment are taken care of, we have to decide where we are going diving. Many people like to wait until the
last minute to schedule their dives and trips. With the number of flight cutbacks since 9/11, you may find that you are unable to get
on the flight you want or that the ticket price is considerably more. Neither of these are good options. Nor are either of
these in our control. Sign up early. Again, you need to get these dates filled in on your schedule. You should look at the trips
that you want to do, the boat dives you want to make, and the special days like Underwater World Day that you want to attend. Then you
need to get these filled in on your calender. You see, if you don't fill in your calender, someone else will fill in those
days for you. Instead of going diving with us, you will be going to a baby shower. That should get you motivated to follow these
instructions. If you have a dive planned, it is easy to say, "Oh, I would like to, but I made previous arrangements." You can click here to
check out our Travel or our Boat Dive schedules. It is also important to find out what
special requirements are necessary for that dive. In the case of travel, is a passport required? Is yours current? Some places will not accept a
passport that expires in the next six months. How current is yours? Diving locally? Outside the quarry you are normally required
to have a dive flag. And some places, like Shark River Inlet, the Coast Guard prohibits diving before 5 pm (too much boat
traffic) and nature prohibits diving anytime but slack tide. So advanced planning is important. Some dive boats require
that you have a pony bottle to dive off their boat. Do you have one? Or at least have a rental reserved?
This is the time to perform some very important checks and it is very important that these checks be performed at the right
time. If you go out after work on Friday night, come home at 11pm and find that your regulator is free-flowing, you are in
trouble. We can be a lot of help at 6pm but at 11pm we are hard to find. So come home from work first and do the following: Put
your regulator on you tank. Check the tank pressure (on both tanks). Just because your tank was full last week, does not mean
it is full today. You may have a slow leaking neck o-ring or blow out disc. Your rotten nephew may have been over and played with
the valve, leaving it slightly open. Or, just maybe, it was mistakenly not filled. We hate to think that those things happen
but they do. Whatever, standing on the boat with a half of tank of air does not make for a good start to the day. Now go breath
off the regulator. (Don't just push the purge button.) Inhale and exhale. Make sure that your computer turns on. Go through
your check list and make sure that you have everything. Then put all your gear except your weights and your tanks into your
dive bag. Put everything together so you can grab it in the morning. Do NOT put your weights behind the door or the sofa so you
do not kick them when you stumble in late that night. If you do, that is where they will be tomorrow when you go to get geared up on
the dive boat. Remember that when you are loading the car in the wee hours of the morning, you are probably still half asleep and
it is easy to forget something.
Well, not really. We still have some planning to do. The first item on your list when you arrive must be the site survey. Are the
conditions safe for the planned dive? Is the surf too rough? Or the currents too strong? Or visibility too low? The best plan
might be to abort the dive right there and then. Don't be afraid to do that. I have on several occasions. Then decide on the planned depth, time and
general direction of the dive. Discuss what action will be taken if you are separated. Don't assume that you know what your
buddy plans to do. Then choose a team leader. This is the diver who will lead the dive. The buddy will follow. This will
greatly reduce the chance that you will become separated. What often happens is one buddy sees something and goes left while the
other buddy sees something and goes right. Both are thinking that the other will follow. Ten seconds later you are separated.
The leader leads!!! This is especially important in three person buddy teams. The problem here is that each buddy thinks the
other buddy has the third buddy in sight. In truth, neither buddy has the third buddy in sight. A very dangerous situation.
It is the responsibility of the team leader to be sure that both buddies are with him.