"Correct Weighting" Identified as #1 Needed Improvement in SCUBA Diving

[The Chairman]

Alternatively, you can let the students use a BC, and just admonish them to stay off the buttons as much as possible.

Sounds like the way I teach already.

 

[boulderjohn]

Better to be over-weighted and clumsy in the water, with a plan to improve, than to be a new diver popping to the surface.

As was mentioned previously, in most cases, it is the overweighted diver who is popping to the surface.

Yes, an underweighted diver will go to the surface at he end of the dive when depleted air has lightened the tank enough. However, if at the beginning of a dive you have enough weight to get down, you have enough weight to stay down. For every extra pound you carry, you must fill the BCD with about 15 fluid ounces of air to balance it out. Eight extra pounds means you must carry about a gallon of air in your BCD to be neutral. All that air is expanding and contracting according to Boyle's law, and that expansion and contraction will make it difficult to control your buoyancy, especially when you are shallow. Divers typically pop to the surface because they are overweighted, go up a little bit during the dive, have the excess air in the BCD expand, and find themselves in an uncontrolled ascent.

When I instruct an OW class, the first time we are in the deep end, I do a demonstration in which I put a random shot of air in the BCD and then go from the bottom of the pool to the top and then back to the bottom (12 feet) using only my breathing to control my depth. I do this while being about 4 pounds overweighted. My lungs are able to overcome the amount of air expansion and contraction in the BCD over that 12 foot range of. (It's about a 40% change at our altitude, BTW.) In contrast, when I practice technical diving in that same pool with steel doubles and other gear, I am significantly more overweighted. The change in that volume over 12 feet is far too much for me to overcome with my breathing. I can only control my depth with that breathing over a range of 2-3 feet. Any more than that, and I have to add air or take air out of the BCD.

 

[Chavodel8en]

I see what you are both saying (overweighted divers tending to be the ones to cork), and as you are instructors, I see that this is based on real experience.

I guess I'm saying that new divers have bad habits (skulling at descent and at the safety stop, failing to completely empty), and a shortcut to counteract those habits is to put extra weight on them. More optimally, an instructor should address those habits and get them closer to their proper weight. That would be the best instruction.

I recognize the instructor took a shortcut, probably bc of the high volume, one weekend in the pool, one weekend in the ocean OW course. While the instructor did purposefully overweigh me, he recognized my bad habits (especially skulling) and instructed me to address them -- I just couldn't fully address them in the weekend I had in the ocean. But he gave me a plan to move forward, and as I became a better diver on my own, I dropped that extra weight.

So personally, I cut this instructor some slack (noting that I did not pay top dollar for the high volume instruction). Instructors who are able to get their students closer to their optimal weight are to be commended.

 

[wetb4igetinthewater]

took a shortcut, probably bc of the high volume, one weekend in the pool, one weekend in the ocean OW course.

I believe this is common. Now I'm probably not anywhere near as good of an instructor as John, as I am limited in my ability to teaching my way effectively to 4 students maximum for 6 hours of pool time. And I'm still experimenting with every class, making tweaks here and there. I will be compensated less initially, but I will have more long term students who invest their time and money into diving (more training, good equipment, local boat dives, and dive trips). That's when I know I have succeeded as an instructor.

 

[boulderjohn]

I see what you are both saying (overweighted divers tending to be the ones to cork), and as you are instructors, I see that this is based on real experience.

I guess I'm saying that new divers have bad habits (skulling at descent and at the safety stop, failing to completely empty), and a shortcut to counteract those habits is to put extra weight on them. More optimally, an instructor should address those habits and get them closer to their proper weight. That would be the best instruction.

I recognize the instructor took a shortcut, probably bc of the high volume, one weekend in the pool, one weekend in the ocean OW course. While the instructor did purposefully overweigh me, he recognized my bad habits (especially skulling) and instructed me to address them -- I just couldn't fully address them in the weekend I had in the ocean. But he gave me a plan to move forward, and as I became a better diver on my own, I dropped that extra weight.

I don't have a problem with an instructor sending a student out a little overweighted and telling them to work on it. To be honest, I usually dive a few pounds overweighted myself. If I have to let out a little burp of air, I don't have to do a gymnastics maneuver to get a tiny bubble to the exit point.

The problem identified here is massive overweighting, and there is a lot of that going on. Lots of people are 10, 15, 20 or more pounds overweighted. A lot of experienced divers are used to being that way, and they advise others. You see it all the time on ScubaBoard threads--people will ask about weighting, and they will get all sorts of friendly advice that seems to me to be about double what that person should need. As I said earlier in the thread, the online weight calculators typically recommend that I wear twice as much as I need.

Here are two stories that helped push me to make weighting and neutral buoyancy an important part of my instruction. Both come from about the time I became an instructor.

1. I was diving in Key Largo, and I saw a young woman struggling in the sand. She was literally crawling on the bottom, her eyes showing that she was obviously not having any fun. When I saw her, I made a vow that my students would NEVER look like that.
2. I got on a boat in Bonaire at the end of a dive. A young woman got on the boat and struggled to walk across to her seat. We saw that her integrated weight pockets were falling out because they had more weight than they were designed to carry. This woman maybe weighed 110 pounds and was wearing a 3mm suit, and she was carrying nearly 30 pounds of lead. Everyone who was on the boat started to talk to her about it. She said her boyfriend, who was still in the water, had told her she needed that much. The people near her quickly took out nearly 20 pounds and told her to do the next dive that way and only tell her boyfriend after it was over. She did it and had a great dive. I did not see her tell her boyfriend about it. I am sure she wanted to wait until they were alone to spare him the embarrassment.

 

[boulderjohn]

Now I'm probably not anywhere near as good of an instructor as John, as I am limited in my ability to teaching my way effectively to 4 students maximum for 6 hours of pool time.

It is not instructor skill. I could not do the full class in only 6 hours, either. It doesn't take me more time than it does to teach on the knees, but I sure can't do the pool sessions in 6 hours and honestly get it all done. The difference in teaching 4 students and 8 students is the number of times you have to be next to an individual student doing a skill. That is the same no matter how you teach. If someone is teaching 8 students in 6 hours, I will bet my life that something is being skipped.

 

[wetb4igetinthewater]

It is not instructor skill. I could not do the full class in only 6 hours, either. It doesn't take me more time than it does to teach on the knees, but I sure can't do the pool sessions in 6 hours and honestly get it all done. The difference in teaching 4 students and 8 students is the number of times you have to be next to an individual student doing a skill. That is the same no matter how you teach. If someone is teaching 8 students in 6 hours, I will bet my life that something is being skipped.

In my OW class, there were probably 10 students or so, one instructor. We had one evening for 4 hours. So many skills were skipped in both the pool and the open water. I shake my head whenever I think about it.

 

[dmaziuk]

I want to expand on this. What dmaziuk wrote is consistent with what I have heard over the many years I have been advocating neutral buoyancy instruction. It is not the only objection I hear, but they all have one aspect in common:

The person who objects to neutral buoyancy instruction objects to it on the basis of something he or she imagines must be true rather than something he or she has seen.

Not exactly but close enough. I'm extrapolating from what I've seen in my own OW class, which is a very limited sample and so the extrapolation is very likely incorrect. I can promise you that there were a couple of students you couldn't get neutrally buoyant on the first pool dive without spending a bunch of extra time on them, though.

 

[wetb4igetinthewater]

Not exactly but close enough. I'm extrapolating from what I've seen in my own OW class, which is a very limited sample and so the extrapolation is very likely incorrect. I can promise you that there were a couple of students you couldn't get neutrally buoyant on the first pool dive without spending a bunch of extra time on them, though.

So having that person lay face down in the water, reg in the mouth, and handing them weights until they float midwater didn't work?

 

[boulderjohn]

In my OW class, there were probably 10 students or so, one instructor. We had one evening for 4 hours. So many skills were skipped in both the pool and the open water. I shake my head whenever I think about it.

There are some instructors who get their people in mid water right from the start. I am not one of them, in part because I have been traditionally very limited by the shop where I worked in terms of the equipment and weights I could use. The other reason is that the start of the class is in the shallow end of the pool, and there is barely enough room for the student to be in mid water. For the first dive in the shallow end of the pool, I have the students lie down on the bottom and put just enough in the BCD so that they rise and fall gently when they inhale and exhale. Their legs or fin tips gently touch the floor, spread comfortably apart. Since I have them pretty close to correct weighting at this point (the true weight check comes later), they don't need much air in the BCD at all. It is important that they be in horizontal trim to the greatest degree possible, so I do not want them in a 45° angle at all. Anyone can do this--it is, in fact, easier then getting them to kneel properly.

Once in that position, the skills go oh-so-much-more-easily. Think, for example, of the reach method for regulator recovery. On the knees, the students are actually tipped backwards a little so they don't fall on their faces. The tank is pulled down and away by gravity. Most cannot reach the regulator, so we end up adding a step that is not necessary in real life--reaching back with the left hand to lift the bottom of the tank so the top gets close enough to reach. When the diver is horizontal instead, gravity puts the top of the tank by the student's neck, and the regulator hose lies right behind the ear, in easy reach for anyone. The skill is completely with ease. All of those first skills are easier and more like real diving in that position.

Once we reach the deep end of the pool, we do all skills in mid water. One of the reasons the whole session does not take as long is that traditionally the most time consuming parts are the later buoyancy exercises. When students have been neutrally buoyant from the start, they get those done much more quickly.