Neutral buoyancy dSMB launch from shallow depth - how hard?

[MaxTorque]

I was in the training pool yesterday, thanks to C19 it's one of the first times i've been back in the pool for a while, and i launched a dSMB from neutral bouyancy at only around 2.5m depth, and frankly, it was messy and fell really hard maintaining my buoyancy! Certainly it would be "no points" from a style perspective.......

I didn't shoot to the surface or bounce off the bottom or anything, but it certainly was NOT a perfect hover style launch..........

Thing is, i've done this a fair few times in open water and not really felt it was too much of a problem,so either my skills are very rusty (definately possible) or it's much harder in really shallow water (worst case of change in volume/expansion with depth).

I was also in my 3mm wetsuit not my drysuit and my trim felt off all dive tbh (as a UK diver, wetsuit is pool or holiday use only ;-)
I have long thin, legs, with little body fat and i felt quite feet heavy whereas in my drysuit i can definately be really pretty horizontal and feet up without too much problem.

Finally i have also changed the way my weights are attached to my rig in order to try to simplify and reduce the bulk of my scuba unit (moved away from integrated dumpable weight system), so that's anther small change

I guess its probably a combo of everything i've just mentioned, but wow, talk about feeling like a learner again!

Anyone got a any top tips for making it easier to do whilst holding trim and depth?

 

[lowwall]

How do you fill the SMB? If it's by exhaling into it, then don't inhale until you let it go.

 

[kelemvor]

@lowwall nailed it. Oral inflate is the way to go. You may be able to get a second breath into it before releasing if you're careful.

Personally, I find inflating at greater depth (usually I do it around 60') much easier. The gas in the SMB expands on the way up obviously, so you don't have to put as much into it when inflating from depth. Of course it must have an OPV if you're going to do that.

If your trim is not right, the whole thing will be much harder as you'll have to continuously compensate for the bad trim. I'd start with making sure your trim is right before working on the smb deployment.

 

[MaxTorque]

Oral inflate yes, requires a completely full lung volume exhale to fill my dSMB at ambient pressure, so at just 2.5m it's still going to be at least 60% of my lungs to fill it.

And yes, release it before taking next inhalation to try to avoid becoming excessively positive is a top tip!

My trim was definately out, i was doing a bit of sideways fin sculling to hold level, and that certainly makes it feel a bit more frantic than just in a stationary hover.

I think also because the pool is just 3m deep, to avoid dropping and hitting the bottom, i was probably just slightly too positive when starting the process, whereas without a hard bottom directly below one, you can drop a little bit and it's no problem, so you can start perhaps a tiny bit negative without any issue. When you are horizontal and the bottom is right there, i also think i over react to changes in height, because it's easy to see the bottom suddenly loom up close. OK, that means it's easier perhaps to see any small changes in height above the bottom but that means perhaps i have (over) reacted more than i would normally do?

 

[Lorenzoid]

Yes, it's harder in shallow water. And oral inflate is the way to go. And it took me dozens of hours of practice to be able to perform this skill to GUE's satisfaction, so don't be hard on yourself.

 

[lowwall]

Yes, it's harder in shallow water. And oral inflate is the way to go. And it took me dozens of hours of practice to be able to perform this skill to GUE's satisfaction, so don't be hard on yourself.

Luckily we aren't in the DIR forum, so 20cm one way or the other doesn't matter

 

[inquis]

Neutral buoyancy is typically at the middle of your breathing cycle, which isn't nearly enough to fill the DSMB at a shallow depth. Your choice of:

• Get neutral at that larger inhale volume by venting a little from the wing first and putting it back when you want to off-load your lungs (i.e., breath normally) after the DSMB is away.
• Slight head down trim and kick to maintain depth to counteract the positive buoyancy induced by your last inhale before filling.

There are pros & cons to each.

 

[BoundForElsewhere]

I was in the training pool yesterday, thanks to C19 it's one of the first times i've been back in the pool for a while, and i launched a dSMB from neutral bouyancy at only around 2.5m depth, and frankly, it was messy and fell really hard maintaining my buoyancy! Certainly it would be "no points" from a style perspective.......

I didn't shoot to the surface or bounce off the bottom or anything, but it certainly was NOT a perfect hover style launch..........

Thing is, i've done this a fair few times in open water and not really felt it was too much of a problem,so either my skills are very rusty (definately possible) or it's much harder in really shallow water (worst case of change in volume/expansion with depth).

I was also in my 3mm wetsuit not my drysuit and my trim felt off all dive tbh (as a UK diver, wetsuit is pool or holiday use only ;-)
I have long thin, legs, with little body fat and i felt quite feet heavy whereas in my drysuit i can definately be really pretty horizontal and feet up without too much problem.

Finally i have also changed the way my weights are attached to my rig in order to try to simplify and reduce the bulk of my scuba unit (moved away from integrated dumpable weight system), so that's anther small change

I guess its probably a combo of everything i've just mentioned, but wow, talk about feeling like a learner again!

Anyone got a any top tips for making it easier to do whilst holding trim and depth?

2.5 meters? isn't it a little late to shoot your dsmb by that point?

 

[Jcp2]

I cheat by having another LP hose with inflator valve available to put air into SMB.

 

[Brett Hatch]

2.5 meters? isn't it a little late to shoot your dsmb by that point?

2.5 meters may or may not be ideal in an open water dive (most likely not). But in the 3m pool, there aren't a lot of options.

@MaxTorque agree with above advice re: oral inflation. I find it much easier to remain close to neutral this way. A couple other pointers come to mind:

* If you are using a big DSMB that you intend to deploy at 10 or 20m, but practicing at 2.5m, you'll have a hard time. Consider either using a smaller DSMB for shallow practice. Or just roll your big DSMB to half or a third its length, and secure it with line, bungee, or a ziptie. You don't have to make a perfect airtight seal here, just tight enough to keep it from unrolling all the way, so that the OPV will open as it ascends

* Before removing your reg from your mouth, have the entire DSMB and reel assembled in your left hand, and the double-ender clipped off to your rig or loose on the line. This leaves your right hand entirely free to hold your reg, which will prevent you from getting anything tangled up. So, right hand removes reg -> extend right arm away from your body -> left hand brings valve to your mouth -> exhale -> fully extend left arm to keep the DSMB / reel away from your body -> right hand puts the reg back in. (Some divers advocate for swapping left and right hand here, so that your left hand is free to work your inflator and deflator. But the same principle of keeping your entire DSMB assembly in 1 hand and your reg in the other applies)

* Once your reg is back in your mouth, if you aren't quite ready to deploy, you can "sip" the air in and out in tiny little breaths without affecting your buoyancy very much

* If you aren't already doing this, consider attaching the reel to the DSMB ahead of time instead of assembling it underwater. This doesn't really have much to do with the shallow water / buoyancy thing, it just makes it easier in general.