Pretty good! Couple things need work, but nice job for a new AOW!
Shooting a bag (DSMB) in strong current conditions
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OP
Hi Jay. Imagine you're removing your Reg from your mouth to inflate the DSMB. A common mistake is to moving the hand/arm away from the head. What happens is the inflated DSMB can loop inside the arm and potentially snag the Reg as it is replaced. The "chin/tuck" is a technique I teach students. When removing the Reg, tuck it under your chin, arm closed (as in the video). This prevents the inflated DSMB from looping in your arm and line entanglement with your Reg as the bag rockets up. Watch the "chin/tuck" portion of the video again. Note that the Reg is neatly tucked under her chin. Now, imagine if her hand was a bit extended and the potential issues this may cause as the bag shoots up rapidly.
On your second question, I start all of my students in horizontal trim. Skills are done in this position and the benefits are immense irregardless of the kind of diving you do (wreck, cave, shallow water reef photography, drift diving, etc). That said, I also teach them that they should feel free to "break trim" as needed. If you feel more comfortable deploying in a vertical position that's fine. Horizontal trim however is the best diving position. Imagine if the diver in the video was deploying in a vertical position. The current would have swept her away. In a Horizontal Trim, she easily held her position.
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CWK
Contributor
I am not a new diver but I was certified 30 years ago when DSMBs did not exist (at least I never saw one at that time). As a result, I have never been taught to deploy a DSMB, which is an essential skill. So finding an instructor, let alone a tec instructor, who is willing to give pointers is a godsend. Thank you!
I have a few questions. Hopefully you do not mind answering them.
On every current dive that I have ever been on, when DSMBs are deployed they are deployed whilst drifting. In a group of 6 or more divers, someone seeking shelter from the current in order to maintain position and deploy a DSMB may mean that the group gets splintered. Why maintain position to deploy a DSMB when diving in strong currents?
She is diving in current and is doing her safety stop, presumably at 5m, in real world conditions. There is a reef below her at the safety stop. Why go to the top of the reef to do a safety stop in current? The video is shot at the Bahura dive site where the top of the pinnacle is at 5m but the max depth is at 25m. Why not do a safety stop along the wall or in the blue? If you are not familiar with the reef, you would not know how shallow it gets. On a different pinnacle, the top of the reef could be 1m, or 2m. Why put yourself on top of the reef at the end of a dive in current?
This is great. Some questions for you with time references.
1:40 She is on her safety stop with the reef below her. I presume that she knows her depth since she is doing her safety stop and is about to deploy her DSMB.
1:57 She unlocks her DSMB
2:04 She checks her computer. The caption says check bouyancy, depth, etc. She is maintaining position with a reef just below her. She is at the same depth as at 1:40 when she began the process of deploying her DSMB during her safety stop. Why look at her computer to check depth?
2:48 She checks her computer again. The caption says check bouyancy, depth, etc. She has been maintaining position with the reef just below her. She is at the same depth as at 1:40 when she started to deploy her DSMB, and also at the same depth when she checked her computer at 2:04. Why look at her computer to check depth again?
2:58 The caption says iron out DSMB. Why waste time ironing out the DSMB? As soon as she blows into the DSMB, the air will rise and straighten the DSMB automatically. She can start with a curled up DSMB, blow into it and it will straighten automatically. What is the advantage ironing out the DSMB before introducing air into it?
3:14 She blows one breath into the DSMB. There is not enough air in the DSMB to impact her bouyancy.
3:20 The bottom of the DSMB can be clearly seen. It is not filled with air.
3:25 She lets go of the DSMB. Why deploy a DSMB with only one breath of air when you are diving in currents? From safety stop depth of 5m, the air will not expend sufficiently to fill a 6 foot DSMB. A small 3 foot DSMB would not be seen from a distance. One breath of air into a DSMB from safety stop depth when diving in currents is puzzling to me. Why.....? Is it adequate?
I would imagine she has learned to check her computer for depth a couple of times so that if she was doing an ascent where the bottom isn’t right there or isn’t visible to monitor her depth, it will be ingrained to stay level when deploying a DSMB. Train for all eventualities.
I only wish back in 1998 when I started diving, my AOW had included a challenging DSMB deployment.
Well done diver and instructor.
I only wish back in 1998 when I started diving, my AOW had included a challenging DSMB deployment.
Well done diver and instructor.
Jay
Need to dive more!
... and re the depth / current, I would assume it's to make life harder on purpose. It's quite a fun skill to practise / learn. I was in the same spot a few weeks back practising 
CWK
Contributor
I forgot to add that after being certified 30 years ago, I stopped diving for 20 years. I resumed diving in April 2017 and came across a DSMB for the first time. I probably purchased my frist DSMB in June 2017 so it is still a new toy, and I have never had instruction in its deployment. Thanks to @Macan, I have the opportunity to some instruction now.
I would imagine that one is usually has bouyancy under control at safety stop before deploying the DSMB. I never imagined that I should check my depth twice between the initiation of DSMB deployment and the end of DSMB deployment.
CWK
Contributor
OP says real world conditions so I'm trying to place it in context.... and re the depth / current, I would assume it's to make life harder on purpose. It's quite a fun skill to practise / learn. I was in the same spot a few weeks back practising
It has been a long time since I was certified. Some things are different now. Like no one attaches a snorkle to their mask now, but it was quite standard 30 years ago. Why would I deploy a DSMB whilst maintaining position at the top of a reef during safety stop in a current dive?
Jay
Need to dive more!
Probably because they're mimicking an alternative environment (shallow, current and no other readily available options) rather then taking the easy path during training. It could also be because their boat crew would be looking for them in that direction. Also, re the unfurling, helps with a smooth execution of the process.
After you give it a go you'll soon find out why all the particulars. There's also few youtube videos, and some pointers in here DSMB & spool purchase - my considerations.
@CWK checking your depth is important. While over a shallow reef you might have an easy visual reference, but in blue water with no bottom and without a visual reference, your depth indication is your computer. By having a student get into a routine of checking depth, means that when they don't have the visual reference of a shallow reef, they will already be checking their depth out of habit. This allows the student to maintain proper depth, it is an indicator if there are any upwellings/downwellings, etc. Knowing your depth is super important. It's a core piece of information that you should be constantly aware of. Simply because you have a visual reference in this particular video, does not mean that every dive will be like this.
As for shooting the bag from the top of the reef, there may be many reasons why this location was chosen for this skill. Sure, they may be able to drop over a wall and shoot a bag from a meter or two lower without any current, but this doesn't put the student in a situation where they are task loaded, it doesn't force them to deal with multiple issues at the same time. The top of the reef may also be the safest place to shoot a bag. You need to quit looking at the situation as a specific dive site with specific conditions, etc. What may be out of the ordinary for this particular spot, may be the standard a mile down the reef. You don't train for the easiest set of conditions, you train for the hardest, so that when you do have to do it in the real world, you're prepared for the worst. These ARE real world conditions that exist, which is why they are training for them.
One breath will absolutely affect buoyancy. Let's say you put a full breath of air in the SMB and DON'T let go immediately. You still have to breathe. So now you inhale, and if you were neutrally buoyant prior, you now have a full lung full of air's worth of positive buoyancy. If a full breath causes you to rise in the water column (which it should, and will if you are neutrally buoyant) 2 lung volumes worth of air will absolutely start an ascent.
This video has real world conditions, but you can't compare a training dive in real world conditions, to every real world dive you would do. Stop looking at this video like it's a random fun dive, it's not. And just because not all of those training steps may be required for the conditions in the video, doesn't mean you should ignore that those conditions exist.
As for shooting the bag from the top of the reef, there may be many reasons why this location was chosen for this skill. Sure, they may be able to drop over a wall and shoot a bag from a meter or two lower without any current, but this doesn't put the student in a situation where they are task loaded, it doesn't force them to deal with multiple issues at the same time. The top of the reef may also be the safest place to shoot a bag. You need to quit looking at the situation as a specific dive site with specific conditions, etc. What may be out of the ordinary for this particular spot, may be the standard a mile down the reef. You don't train for the easiest set of conditions, you train for the hardest, so that when you do have to do it in the real world, you're prepared for the worst. These ARE real world conditions that exist, which is why they are training for them.
One breath will absolutely affect buoyancy. Let's say you put a full breath of air in the SMB and DON'T let go immediately. You still have to breathe. So now you inhale, and if you were neutrally buoyant prior, you now have a full lung full of air's worth of positive buoyancy. If a full breath causes you to rise in the water column (which it should, and will if you are neutrally buoyant) 2 lung volumes worth of air will absolutely start an ascent.
This video has real world conditions, but you can't compare a training dive in real world conditions, to every real world dive you would do. Stop looking at this video like it's a random fun dive, it's not. And just because not all of those training steps may be required for the conditions in the video, doesn't mean you should ignore that those conditions exist.
In a strong current, I always deploy my DSMB from depth, while drifting. The videoand the student are excellent, but why make it so difficult?
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