Quiz - Skills & Environment - Overweighted Diver

[Scuba-74]

I've heard a lot of people say it's better to be overweighted than underweighted. I tend to disagree, because an underweighted diver can quickly diagnose and solve the problem before the dive begins, but an overweighted diver deals with the consequences of his or her problem for the entire dive.

As a matter of fact, you can't quickly diagnose and solve the problem of being underweighted before the dive begins. Proper buoyancy check is done with an empty tank. A diver may be perfectly capable of submerging in the beginning of a dive, and then have tons of issues with a safety stop, especially if there is some current or wave action.

 

[Scraps]

This is certainly a popular statement. But how true is it? Is there real evidence for it? Or is it just in the category of,
"Face mask on your forehead means you are panicked."

Fair question. I don't know how prevalent it is.

I took the open water course twice: PADI in 2002 and NAUI in 2017 after not diving for 14 years. Both times, all students were overweighted. My daughter took SSI's open water through her college last fall and didn't know how to conduct a weight check when I dove with her afterward.

However, the LDS where I took my DM course and occasionally help with classes spends a good bit of time on how to do a proper weight check.

 

[Scraps]

As a matter of fact, you can't quickly diagnose and solve the problem of being underweighted before the dive begins. Proper buoyancy check is done with an empty tank. A diver may be perfectly capable of submerging in the beginning of a dive, and then have tons of issues with a safety stop, especially if there is some current or wave action.

Fair point, and I thought about putting a discussion of safety stops in my post. But you can do a weight check with a full tank. You do it by the book, then add extra weight equal to the expected change in your tank's buoyancy.

 

[tursiops]

Fair point, and I thought about putting a discussion of safety stops in my post. But you can do a weight check with a full tank. You do it by the book, then add extra weight equal to the expected change in your tank's buoyancy.

Better to add weight equal to the maximum change in your tank's buoyancy....for example, 6 lbs for an AL80. Many say 5 lbs, but if you actually go below 500 psi then you will be buoyant. not nice at a SS!

 

[scubadada]

...an underweighted diver can quickly diagnose and solve the problem before the dive begins....

The only proper weight check is at your safety stop, or last deco stop, and on your final ascent to the surface. As an example, with an AL80, you will be a little over 5 lbs lighter at the end of your dive with 500 psi than you were at the start with a full cylinder. You could easily be underweighted at the start of the dive and then not be able to hold your stop at the end.

Edit: sorry, @tursiops and others were posting, while I was typing

 

[Scuba-74]

Fair point, and I thought about putting a discussion of safety stops in my post. But you can do a weight check with a full tank. You do it by the book, then add extra weight equal to the expected change in your tank's buoyancy.

That's a fair point too.

Another point that comes to mind, is there a definition of a "proper" weighting? If it's the amount of weight that allows a diver to pass a buoyancy check by the book on the surface, then it doesn't account for several important attributes of a dive, such as currents, or water temperature. If I'm doing a drysuit dive in a cold water, I may need to keep more air in my suit just to stay warm, and would need more weight to compensate for that.

So, if we adopt what most would consider to be the definition of "overweighted", then I would argue that there are indeed scenarios when it's better to be overweighted than underweighted.

 

[Scraps]

I think we’re nitpicking here over something we generally agree about.

From the discussion, it’s apparent that we all understand that our buoyancy changes during a dive. One can be “exactly” correct at only one moment in a dive, and it’s best for that moment to occur around the end of the safety stop or later.

As a result, we all accept the prudence having enough extra weight at the beginning of the dive to be right at the end of the dive.

But that’s not what this question is about and it’s not what my comment was about.

The question was about carrying so much extra weight that it affects one’s ability to dive, and my comment was about the a) the practice of deliberately overweighting students to the point that they can’t hover without having a good amount of air in their bc’s, and b) the unequivocal position that overweighting is better than underweighting.

It’s not uncommon for me to see people much smaller than my 100+ kg of bodily mass wearing more than twice as much weight as I carry.

Achieving proper weighting requires constant dialing in and constant adjustment with each change of equipment, environment, and body weight.

The “overweighting is better than underweighting” mindset gives some divers an excuse not to do that dialing in, but also prevents them from achieving proficiency.

 

[TMHeimer]

This one has a pretty clear answer, as shown by the vote count. "A" could be correct if it was added: easier to make safety stop than if you're underweighted". That also may possibly be determined by how much overweighted--2 pounds? 25 pounds?
Begs the question "easier than what?-- correctly weighted (no) or underweighted (yes).
Here I am, again Mr. Picky....
But, only one person so far seemed to be confused.

I really like Scraps' post, especially about only being exactly correctly weighted at one moment during a dive. First time I've read anyone else but myself mention that on the board.

 

[Angelo Farina]

One can be “exactly” correct at only one moment in a dive, and it’s best for that moment to occur around the end of the safety stop or later..

Well, this depends on the diving profile. If, as the tank empties, you go deeper, squeezing your suit, you keep the same buoyancy, so you can stay in neutral buoyancy in multiple pairs of air content - depth.
Of course when you will come up you will become significantly positive, but this could even be acceptable, if the dive was significantly within NDL, and no "safety" stop is planned...
My point is that buoyancy is affected in opposite ways by the tank which is emptying and by the suit which is compressing as you go deeper.
When I started diving there was no BCD, no safety stop, and the recommended diving profile did not assume a fast descend and a slow ascent. hence it was quite standard to use very little weight, and dive as described above, staying more or less neutral for most of dive.
Of course, being so buoyant, for going down the first 4-5 meters it was necessary to employ a free-diving technique, called "capovolta" in Italian (I do not know the exact English translation of this manoeuvre). Learning to do it was a significant prerequisite for becoming a scuba diver...

 

[Scraps]

Angelo,

capo - head / volta -turn / capovolta: somersault.

Was the capovolta maneuver akin to what we call a surface dive in the skin diver course?

Addressing your other point:

Let's assume there is a point during your descent when your bodily and carried weight, the buoyancy of your tank, and the compression of your suit balance out to make you perfectly neutral. Let's assume this point happens at 20 meters.

What happens next? You continue breathing, so your tank will get lighter. You can continue to go deeper, but your suit can compress only so far. Half of the possible compression took place in the first 10 meters of your dive. After that point of perfect weighting, going deeper will increase the rate at which you add buoyancy to your tank, but the rate at which your wetsuit compresses will decrease. The continued compression of your wetsuit won't keep up with your increased air consumption. At any time after that point, you will be underweighted.