- Ladies and gentlemen, what's going on?
Welcome to Scuba Diver Magazine.
My name is James and I am Scuba Diver Magazine's
Man in Miami.
Scuba Diver Magazine has brought me over
from my own channel, Divers Ready
with one simple goal in mind
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This week is the next video in our series
that we like to call, Dive Like A Pro.
And we're focusing on weighting.
Later in this video, I'm gonna be giving you
my one single piece of advice
for getting your weighting absolutely perfect,
like a professional diver.
But first, I'm gonna answer the five questions
that I get most commonly as a dive instructor
concerning the amount of weight you need to go scuba diving.
Starting with, why is proper weighting so important
for successful diving?
Being correctly weighted is absolutely essential
because having the right amount of weight on you
ties into your ability to perform the four core skills
of scuba diving that we've been talking through
throughout this series of Dive Like A Pro.
If your over-weighted, you're gonna need
to put more gas through your buoyancy compensating device
which is gonna increase your gas consumption,
which is gonna mean that your buoyancy will be off
and you'll constantly be fighting an up down kind of battle.
If you have the weight incorrectly dispersed
around your body, your trim will be off.
If you have too much weight,
you're gonna have to kick harder than you should have too,
which is gonna mean your finning will be off balance.
If you don't have enough weight,
you're gonna be constantly fighting to get down.
If you're over-weighted, you're gonna be working harder
which means your breathing rate is,
there's hundreds of reasons
why you're weighting needs to be spot on.
It's an essential skill of scuba diving.
And as I said before, it ties to the pillars
of your scuba diving ability.
Next question I get, dive gear is heavy,
why do I need any weight at all,
won't I sink with just dive gear on?
No, you won't, because Archimedes says you won't.
In about 250 BC, the Greek mathematician Archimedes
laid down the law for what is basically
an essential principle for all scuba divers.
And that is an object wholly or partially submersed
in the liquid is buoyed up by a force
equal to the weight of that liquid displaced.
So even though yes, scuba diving gear is heavy,
it's also bulky, and what we're focused on
is not weight but density.
So if you have big bulky gear as heavy as it is,
it's still gonna displace a lot of water
and that needs to be compensated against
using something that is incredibly dense
in terms of a lead block.
And I hope none of you have ever thought
about getting in the water without weight,
but if you did, you'll notice it was very hard
to go scuba diving.
Even in bulky, heavy dive gear,
a normal human being cannot get themselves under the water
without the assistance of lead.
Scuba diving without lead is just expensive snorkeling.
So we add enough weight to get us under the water
and then add gas to our BCD
to make sure that we're not knuckle dragging
across the sea bed.
Next question I get asked all the time
as a dive professional is, how much weight do I need?
Well, unfortunately there's no easy answer
or equation for this.
I can't take your body weight and add the weight
of your gear and divide by the first number you think of
and come up with the right amount,
because a lot of it has to do with the composition
of your body type.
Add to that the different densities
of the gear choices that we make,
and it's not really a cut and dry answer.
Still, the best way to figure out
how much weight a diver needs is trial and error,
it's to get in and do a weight check,
more on weight checks a little bit later on,
and refine it until you get the minimum amount of weight
that you actually need.
Personal buoyancy plays a big part
in how much weight you need to go scuba diving.
And the best study that was ever conducted
on personal buoyancy was done actually by a swim coach
from Georgia Tech called Fred Lanoue in the 1960s.
And he published a book called
"Drownproofing: A New Technique for Surviving in the Water."
His concern was obviously keeping swimmers safe and buoyant,
and he did probably the most expansive research
on how floaty or sinky,
buoyant, a human body actually is.
Not in like a creepy throwing corpses
in a swimming pool kind of way.
The summary of his study,
I'll save you reading it, 'cause it's pretty dry material,
is that humans ranged from about seven pounds
positively buoyant, seven pounds floaty,
to about five pounds negatively buoyant or sinky
as he referred to them.
Not sure you can call people sinky, is that,
I'm sure it's gonna offend somebody.
In order to understand personal buoyancy
as Fred Lanoue studied it,
you just need to understand that the different tissues
that comprise the human body have different densities
and therefore different buoyancy attributes.
Bone is incredibly dense but as you get older,
it gets less dense.
Muscle is incredibly dense.
Think about two glasses of water,
you put a lump of butter into one
and a lump of steak into the other,
the steak sinks and the butter floats.
So your personal body composition will tell you
where you lie on that seven pounds positive
to five pound negative scale.
And then in addition to your personal buoyancy
you need to consider your equipment
when trying to figure out how much weighting you use.
Whilst all your equipment choices
have some effects on your buoyancy underwater,
there are really three pieces of kit
that change your buoyancy as the dive progresses.
The first obviously is your BCD,
your buoyancy compensating device,
which you need in order to make adjustments
based on your other gear.
So I'm not gonna focus on that too much
but think about the other two, starting with your tank.
First off, all tanks, whether they're steel or aluminum,
become more buoyant as the dive progresses
because you're consuming gas from them.
So you're making the tanks lighter,
yes, gas does have a weight value, significant weight value.
And as you consume the gas, the tank gets lighter,
which means it gets less dense,
which means it becomes more positively buoyant.
Now, if you have a steel tank, it is unlikely
that even though it will become more positively buoyant,
it won't tip over to the point of being actually buoyant.
That's not true of aluminum tanks.
If you take a standard AL80, for example, 80 cubic feet
or 11.6 liters in metric.
As you consume that tank and you get it down to around,
I wanna say, 1300 PSI, I think it's just shy of 100 bar.
That's the tipping point where they go
from being negatively buoyant
to start becoming positively buoyant.
And then as you drain the tank further and further down,
the more floaty the tank becomes.
So you need to take that into account
to make sure you've got enough lead for the end of the dive.
More on that later.
The third piece of equipment you need to consider
is your thermal protection.
There is a huge difference between diving
in a rash guard and shorts and a dry suit.
And the reason for that difference is displacement.
A dry suit is a lot bulkier, it takes up more volume,
it displaces more water,
which means you need to add more lead
to overcome that buoyant factor.
Even a couple of millimeters difference
in the thickness of wetsuits, when spread over the area
of your whole body is gonna make a huge difference
to the amount of water that you displace.
But not only that, but wetsuit material changes
its buoyancy characteristics throughout the dive.
At the start of your dive, on the surface,
the wetsuit is at its maximum thickness.
As you descend and ambient pressure increases,
the neoprene that your wetsuit is made out of
actually compresses, which means as you get deeper,
your wetsuit becomes less buoyant,
And then on ascent, the reverse happens.
The pressure releases, the wetsuit expands
and you become more buoyant,
which means your rate of ascent,
if not controlled properly, will accelerate.
And the third factor to consider after personal buoyancy
in your equipment choices is the water type.
Salt or fresh water.
If you're going from fresh water to salt water,
you will need to add lead because salt water
is more dense and vice versa going the other way.
So, James, how do I conduct a weight check?
Well, very easily, in five simple steps.
Ready, here we go.
Step one, get kitted up,
guess the amount of weight you need,
make a giant stride entry into the water,
having completed a buddy check first of course,
and then once on the surface,
breathe in a medium deep breath and hold it.
Step two, raise your inflator over your head,
tuck your other arm in and cross your ankles.
The reason you do those two things
is to resist the temptation to scull or kick.
You wanna be perfectly stationary.
Step three, release all the air from your BCD
and you should float at eye level,
still holding that breath.
If your BCD is empty and your chin
is still out of the water, you don't have enough lead.
If your BCD is empty, you're still holding
that normal breath and you're sinking past eye-level,
you have too much weight.
Step four, breathe out, you should start to sink.
Don't kick, just let yourself go down.
If you don't find yourself sinking,
you don't have enough weight.
Step five, you may wanna add an additional two pounds
if you're using an aluminum tank
because obviously your tank is full
at the beginning of the dive,
and at the end of the dive, it won't be full.
And you're gonna have to fight that positive characteristic
of that type of cylinder.
If you're diving steel, don't worry about it,
just go enjoy your dive, have fun, job done.
Okay, next question.
Why do some divers struggle with their weighting?
It's true, I see this all the time on dive boats.
I'll be minding my own business kitting up
and the dive master will be going around the boat
and asking how much weight people need.
And I'll see somebody who's much smaller than me
and is diving in just shorts and a rash guard,
and doesn't appear to be in any way bulky,
diving, nice small gear.
And they'll ask for like, 10 kilos or 22 pounds of lead.
It's a common mistake to think you need
more lead than you do,
and as I said at the start of this video,
that's just a really inefficient way to dive.
Although this series is called Dive Like A Pro,
it could possibly be a professional diver's fault
that you think you need more weight than you do,
because some less reputable dive instructors out there,
instead of taking the time to get their students
right with their weighting
as they're going through the open water course,
will just sand bag them,
just leaden them like a desert camel
with as much weight as possible.
Because...
Well, it's kinda like walking your dog
on a short leash, really,
if you have the dog under control,
you know where they're gonna be
and the same thing with divers underwater.
If you take your eye off a diver for a short while,
it's normally better that on a shallow training dive
that your diver is in the sand at the bottom, 30 feet down,
rather than shooting to the surface
and bobbing around in boat traffic.
It's not right, I don't do it, I don't support it,
but that doesn't mean it doesn't happen.
If your dive instructor did that to you,
and has convinced you that you need more weight
than you actually do,
I suggest you go back to them and ask for your money back
or make them teach you properly.
Ultimately though, once you're certified,
it's down to you to refine the amount of weight you need
and get it down to the absolute minimum
that you can actually dive with safely and under control.
Right, well, that answers the five most common questions
that I get as a dive professional about weighting.
And now it's time, as has become our habit
with this series of videos, for me to give you
my one single biggest piece of advice
to help you get your weighting correct.
And that is, do a confirmation weight check
at the end of your dive.
Think about the end of your dive,
your tank is the lightest.
Your wetsuit, if you're using one
is gonna be at its thickest,
it's gonna have re-expanded after your dive,
and you're gonna be the lightest you're gonna be
at any point during that dive.
So it's actually more important
that your correctly weighted
when you're trying to hold that five meter,
15 foot safety stop and get your buoyancy really on point,
that weighting is correct then.
You wanna make sure that at the end of the dive,
you're not shooting up to the surface
and you're correctly weighted for your safety stop.
So a confirmation weight check at the end of a dive
is a very useful way of doing that.
Here's how you do one in four easy steps.
Step one, ascend to your safety stop and hold a tight hover.
Step two is hold your safety stop depth
and breathe your tank down,
keeping a really close eye on your gas
to just above your reserve pressure.
I'd recommend doing this after you've completed
your safety stop so you can surface immediately afterwards.
Then step three is to offload portions of the weight
that you're carrying.
I personally recommend using small increments of weight.
If you can get those little lead pellet bags
that come in like half pound or one pound increments
that can really help you refine the exact amount of weight
that you need to go diving.
If you're not doing your safety stop
on like a nice sandy ledge
where it's easy to put small amounts of weight down
and then retrieve them later,
I recommend just putting them in your buddy's BCD pocket
when they're not watching.
Once you've offloaded as much weight as you can
without floating up,
that is the minimum weight you need to complete the dive.
So think about it, your tank is at its absolute lightest
and you have the minimum amount of lead.
And then step four, you'll still be able to breathe
naturally and hold neutral buoyancy
with that amount of weight
and the lightest tank and your wet suit,
If you're using one, at its thickest.
And then once you've retrieved the little weight
and you've made a safe surface and exited the water,
you can make a note of how much weight you were able to dump
and still stay neutrally buoyant
with a very light scuba tank.
And you know what the exact amount of weight is
you need for subsequent dives.
Ladies and gentlemen, I hope you learned something
from this video and I hope you enjoyed the content
that we're putting out.
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about one thing and one thing only,
making you a better, more well-informed diver.
I thank you so much.
Just over here, I'll put some other videos
that I've made for Scuba Diver Magazine
that you can check out.
And in the description of this video below
is a link to my channel Divers Ready,
where we have a ton of videos aimed at helping you
become a better scuba diver.
So feel free to head over there
and check out more content from me.
Until next time, ladies and gentlemen,
my name's James, Scuba Diver Magazine's Man in Miami.
Thank you so much for watching,
dive safe, dive often and dive like a pro.