Shooting a bag (DSMB) in strong current conditions

[CWK]

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.

I was diving Derawan island in January. My last dive was a at a site called Lighthouse off Derawan a couple of days after the January supermoon. Anyway, the crrent was slight at the start of the dive but picked up as the dive progressed. We ended up drifting pretty quickly at the top of the reef. No worries. Everyone who deployed a DSMB did so while drifting on top of the reef. No real need to seek shelter to stay in position.

My own self taught method for deploying a DSMB does not require unfurling. I prefer the DSMB to be compact in front of me instead of being unfurled to the side, which it would be if I were to iron it out with my hand. Just introduce air and let it go. It is self straightening. To me unfurling it is a unnecessary complication.

 

[CWK]

@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.

I am familiar with vertical displacements. During my last trip to the Maldives in Feb/Mar this year, I came upon vertical displacements 3 times (2 up and 1 down).

In my experience vertical displacements occur near walls. In such circumstances, the wall provides a visual reference for depth. I have not come across vertical displacements when I am away from the wall or in the blue. Vertical displacement in the blue is possible if two oceanic currents converge but I think these are generally really far from land. Have you experienced vertical displacements in the blue? If so, are you able to explain what caused the vertical displacement?

I check my depth and ensure that I have my bouyancy under control before I move a muscle to initiate DSMB deployment. Once I initiate DSMB deployment, my focus is to let go of the DSMB as soon as possible. I check my depth again once I have released the DSMB. I prefer to do my depth check on either side of a quick DSMB deployment.

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.

I get deploying a DSMB from the top of a reef an I have been in this situation. See my previous post.

I do get making things tough in a training exercise. But OP says real world conditions, and to me, there is generally no need to maintain position in a current for deployment of a DSMB.

[QUOTE="JohnnyC, post: 8259207, member: 429324"][USER=488098]
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.[/QUOTE]
1 lung volume into the DSMB does not affect overall bouyancy. I think we are agreed on that. I agree that inhaling the second lung full of air without letting go of the DSMB would affect bouyancy.

Diving in currents, I would want a 6' DSMB, or at the very least a 5' one. To me, a single breath of air into a DSMB at 5m is just insufficient. The DSMB would not inflate sufficiently. If you want to train the diver for a real world situation, perhaps teach the diver to inflate an appropriately sized DSMB with sufficient air?

[QUOTE="JohnnyC, post: 8259207, member: 429324"][USER=488098]
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.[/QUOTE]
I look at it as a training exercise. This is a training discussion.[/user][/user]

 

[iamrushman]

i watched the video...good work by the diver and thanks for sharing.

 

[BertStevens]

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?

Training is about muscle memory. Doing the same thing over and over so it becomes automatic. It’s not about making it difficult. It’s about teaching a valuable skill in a real world, yet semi controlled environment so that it can be repeated in a difficult uncontrolled environment.

Maverick, from Top Gun: “You don't have time to think up there. If you think, you're dead.”

There may come a time when the diver is so task loaded, they dont have time to think. Having trained the muscle memory, the task will happen without thought.

 

[DawgFan]

This is a video of my PADI AOW student learning how to deploy a DSMB in strong current conditions while maintaining position (vs drifting).

I thought I'd share this with the community to help new divers learn this essential skill. The video includes a step-by-step "how to" of the skill starting at 1:40.

The student in the video is learning so don't expect perfection . Also, the video was shot in real world conditions (strong currents while on a safety stop) vs. a photo shoot in a pool or perfect ocean conditions . Watch it in HD to see the details of the skill.

I hope this helps someone.

Impressive. Do you know what type fins she has? I have similar low cut boot and soft adjustable fin strap like she has but my fins are best for flutter. I've been looking for a fin that will allow me to frog kick and flutter but with a soft adjustable strap like the one's your student has. The fins with spring straps and bungees don't do well with my old heels.

 

[Macan]

Impressive. Do you know what type fins she has? I have similar low cut boot and soft adjustable fin strap like she has but my fins are best for flutter. I've been looking for a fin that will allow me to frog kick and flutter but with a soft adjustable strap like the one's your student has. The fins with spring straps and bungees don't do well with my old heels.

Hi, the diver in the video is using one of my rental fins only because it fits her . It's a Taiwan made fin called Unidive. Choosing the right fin is a separate thread altogether . I recommend spring straps over soft adjustable straps. Easier to put on and remove. I suspect the problem you have is the spring strap you tried is too small. Try the next larger size spring strap. It will pleasantly surprise you .

 

[CWK]

Training is about muscle memory. Doing the same thing over and over so it becomes automatic. It’s not about making it difficult. It’s about teaching a valuable skill in a real world, yet semi controlled environment so that it can be repeated in a difficult uncontrolled environment.

Maverick, from Top Gun: “You don't have time to think up there. If you think, you're dead.”

There may come a time when the diver is so task loaded, they dont have time to think. Having trained the muscle memory, the task will happen without thought.

I get task loaded training. I think appropriateness of equipment and task are also important in training. I would task load and sequence some elements slightly differently. And I also value speed.

Some thoughts:
- Horizontal trim: OK. I think maintaining trim throughout a dive is good.
- Frog kick: Yes. Alternative finning methods are good.
- Depth check: How often does a diver check depth during a dive? I would say sequence the depth checks to the beginning as well as end of the DSMB deployment, instead of mid-way.
- Overhead check: I usually check that there is no diver above me before I initiate DSMB deployment. Perhaps an additional element to task load a student?
- DSMB: She is perhaps 5' and the DSMB is shorter than she is. I think it is the OMS 1m hybrid SMB that she is using. I'd want a DSMB that is visible from a distance. An appropriately sized SMB/DSMB, say 6' long, for diving in currents perhaps? I've seen 10' DSMBs in action but I think 6' is more appropriate in a training situation.
- Oral inflation of DSMB with chin tuck: In the real world, 1 breath of air into an approrpiately sized DSMB is insufficient at 5m. At 40m perhaps 1 breath may be sufficient for a 6' DSMB. Why teach this technique to a AOWD at 5m? Why not teach DSMB inflation with a regulator?
- Speed: Speed is an important element in deployment. From clipping off her double ender at 0:11 she takes 39 seconds to prepare her DSMB for inflation which occurs at 0:50. This is too long. Perhaps aim for 20 seconds? She begins inflation of her DSMB at 0:50 and she releases at 0:59. I use a semi-closed DSMB and the interval between inflation (with a regulator) and release is about 2 seconds.
- L-line sweep: I am not certain that this helps avoid line entanglement.

I'm newly self-taught in the art of DSMB deployment. I've never read what the manual says about how a DSMB should be deployed. Where am I going wrong?

 

[Macan]

HI CWK. Thanks for your comments and questions. @JohnnyC and others have given great answers and as the OP, I thought I’d add a few points.

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?

• It is easier to drift with the current and shoot a bag. But there will be situations wherein you have to hold your position, in strong currents, and deploy a DSMB. This is what the diver in the video was training for.

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?

• Good training is progressive, builds on basic skills and filled with repetition . Checking and correcting for depth, trim and position is essential for safety and overall situational awareness. It teaches a diver not to be task fixated. A diver multi-tasking, task-loaded and intently focused on executing a complex skill (eg deploying a DSMB) can quickly lose control of buoyancy/depth if left unchecked. While the diver in the video made it look easy to maintain depth/position, it's not. The diver was constantly correcting .

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?

• An opened (unbungeed) DSMB has a mind of its own haha . It will snake all over you and it loves to loop around your hoses . Revisit the video at 2:47, the opened DSMB flowed with the current beneath the diver. If the diver inflated the DSMB at that point without ironing it out, the DSMB could have loop through the hoses as it rockets up and the line can snag the hose or the regulator, pulling the diver up with it. Additionally, if the DSMB is not ironed out (ie remains rolled up), it’s harder and requires more effort to inflate for obvious reasons.

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 trained and grew up with 6+ foot open-ended DSMBs in the 90’s. For underwater deployment, I don’t use them anymore. They’re too big, imprecise, requires more air and effort to inflate, unforgiving of incorrect deployment, etc. 6ft DSMB have a place - surface deployment, but not underwater. I carry and teach students to bring a 6ft DSMB (I keep mine folded in my backplate) but to only deploy it on the surface if needed. For underwater deployment, I teach and use a 3.3 ft (1 meter) closed-ended DSMB as seen in the video.

• The DSMB in the video is a 3.3 ft DSMB, not a 6 ft DSMB. As the DSMB rises, air will expand . Yes, the diver in the video could have added just a little bit more air . That’s why it’s a training dive .

 

[Macan]

- L-line sweep: I am not certain that this helps avoid line entanglement.

If you try to deploy a DSMB in strong currents and hold it in front of you, the line will angle steeply (diagonal to the strength of the current) and potentially snag your first stage . The L-Line Sweep in not in any text book/manual, it's just a technique I came up with to teach students to avoid line getting tangled on their first stage.

 

[CWK]

Hi @Macan,
Many thanks for your response.

• An opened (unbungeed) DSMB has a mind of its own haha . It will snake all over you and it loves to loop around your hoses . Revisit the video at 2:47, the opened DSMB flowed with the current beneath the diver. If the diver inflated the DSMB at that point without ironing it out, the DSMB could have loop through the hoses as it rockets up and the line can snag the hose or the regulator, pulling the diver up with it. Additionally, if the DSMB is not ironed out (ie remains rolled up), it’s harder and requires more effort to inflate for obvious reasons.

I think ironing out a DSMB is not required, but that is only my way of thinking. Perhaps see the following as just one example of introducing air into a DSMB that is still furled. Not the best video but the idea is there:

• Good training is progressive, builds on basic skills and filled with repetition . Checking and correcting for depth, trim and position is essential for safety and overall situational awareness. It teaches a diver not to be task fixated. A diver multi-tasking, task-loaded and intently focused on executing a complex skill (eg deploying a DSMB) can quickly lose control of buoyancy/depth if left unchecked. While the diver in the video made it look easy to maintain depth/position, it's not. The diver was constantly correcting .

Agree checking depth is essential. My suggestion was to place this check at the beginning and end of DSMB deployment, not do away with it. My focus is on speed of deployment, cutting out unnecessary like ironing . But that is only my way of thinking. I would ideally like to release a DSMB within 20 seconds.

• I trained and grew up with 6+ foot open-ended DSMBs in the 90’s. For underwater deployment, I don’t use them anymore. They’re too big, imprecise, requires more air and effort to inflate, unforgiving of incorrect deployment, etc. 6ft DSMB have a place - surface deployment, but not underwater. I carry and teach students to bring a 6ft DSMB (I keep mine folded in my backplate) but to only deploy it on the surface if needed. For underwater deployment, I teach and use a 3.3 ft (1 meter) closed-ended DSMB as seen in the video.

I don't lean towards open-ended DSMBs. I prefer semi-closed or closed. For semi-closed I'd use a regulator for inflation. For closed, I'd use a low pressure inflator rather than oral inflation. I also prefer to only have one DSMB. I have more than enough equipment to carry.

If you try to deploy a DSMB in strong currents and hold it in front of you, the line will angle steeply (diagonal to the strength of the current) and potentially snag your first stage . The L-Line Sweep in not in any text book/manual, it's just a technique I came up with to teach students to avoid line getting tangled on their first stage.

She did the L-line sweep after replacement of regulator in her mouth. If you hold the spool out in front of you, the current has to be extremely, extremly strong to get the line anywhere near the regulator. I'll keep it in mind though.

Thanks again for the tips. Much appreciated.