Using a closed-bottom DSMB/Lift Bag

[inquis]

It's more about thinking through how to actually use this thing without a wild ride up

Stay horizontal for greater resistance to acceleration. Commit to jamming the inflator hose on, exhale hard to help offset the buoyancy increase, and let go after a sufficient # of mississippis (depth dependent as stated above). You don't have time to "inspect for fullness".

 

[DiveLikeAMuppet]

Some of them maybe. The one I have has something >50# lift. It's about 6ft long and has a circumference of about 16-1/2 inches. Their current issue that's the similar or the same as mine is spec'd to have 52# lift
Not all that much, I suppose for doing serious salvage work, but it seems like a lot when I'm trying to fill it up before letting go

Oh Halcyon finally made a proper DSMB, I didn’t know You definitely are not deploying that from the shallows with enough gas unless you hold onto something. 20-25 meters will be OK if you can use an inflator. What I would do is put a small squirt of gas in, let it unroll and check that it’s clear and fill about 1/3 with with inflator and quickly let it go, it’s a lot of lift to manage.

 

[Edward3c]

ha ha, yeah I suppose I knew that. Guess I worded my question poorly...(english is hard for an engineer, after all..)

It's more about thinking through how to actually use this thing without a wild ride up...or if it even can be used from a shallow depth

The only way you're going to get a fully inflated DSMB it to secure it to the bottom, inflate then let it go.

When I let mine go from 6m I'll normally complete the fil at the surface, if I need to.

 

[bradlw]

and let go after a sufficient # of mississippis

In practice, about how many Mississippi's do you think it takes?
I'm going to play with it some more the next time I get back into the water with the right conditions...

Oh Halcyon finally made a proper DSMB, I didn’t know

I think they've had it since "the beginning" (well I don't really know when the beginning for them was, but still).....I bought mine around about 24-25 years ago when I bought my single-tank BP/Wing set-up. Pretty sure it was the only one they sold back then.(??) I want to say they had some bigger lift bags, but as a marker I remember it as being the only one. Long time ago so I'm probably wrong.....

 

[Rebreather Rabbit]

For me, I wind up doing the 'technical' thing with a DSMB, launching it right before I start my final ascent as long as visibility allows it. Makes it easier to 'fully fill'.

Unfurl it, puff a bit of air into it to get it to straighten and pull upward, look up to verify nothing above you, then fill till it's making you ascend while trying to stay negative (exhaling and the like).

I personally use a spare LPI hose and the inflator stem. I used to fill it from the bottom using a spare regulator, but it's one more thing to juggle and usually wastes at least some gas while trying to get the mouthpiece far enough into the duck-bill. I find using a LPI hose much easier.

Regarding the chatter about how often they are really used, it all boils down to the location, type of diving, and what the boat captain or dive leader wants to see.

 

[Rich1280]

I fill mine from my drysuit hose, use it on most dives. About 20m is a good depth, or slightly deeper. Shallower just needs more gas in it.

As others said, I get it out and hold the spool and DSMB in my right hand, then disconnect my drysuit with my left hand and manipulate it so I put a tiny squirt of gas in the DSMB to stand it up. Then quick look up, breathe out a big breath and head down slightly to be able to put a little kick in if needed and fill it properly for the depth with the LPI. Commit to the connection! This is usually about 2 seconds I find to get a nice firm one.

Achim has a good video, but where he oral inflates I use the LPI.

Rich

 

[bradlw]

Then quick look up, breathe out a big breath and head down slightly to be able to put a little kick in if needed and fill it properly for the depth with the LPI. Commit to the connection! This is usually about 2 seconds

makes good sense...very helpful. Thank you

for perspective on that 2-seconds.... how big is your DSMB?

 

[Rich1280]

makes good sense...very helpful. Thank you

for perspective on that 2-seconds.... how big is your DSMB?

I've got a Halcyon 6ft slim. Got a 6ft fat at home i use for certain things, but the 6ft slim seems to be the right balance. I seem to think the 6ft fat was about 3 seconds at 21m.
Rich

 

[happy-diver]

Come on man, buckle and buy one of these brilliant uncool but ingenious things

Post in thread 'Using a closed-bottom DSMB/Lift Bag'

Aug 10, 2025

Splitter for me, never had any issue with it. But, as said, generally oral inflate. I could put a short hose from the splitter if I wanted to. DGX has a similar piece now to the one below, a little chunky but okay (the splitter below comes from back in the 70s or 80s, it may have been Dacor, frankly do not remember):



The air pressure blows the mouth piece out, release and away it goes. I am pretty much clutter free so not much to entangle on.

• Nemrod

• 
• 

I fill mine from my drysuit hose, use it on most dives.

 

[Nemrod]

I note that Achim is using a pre-rigged 1 meter (3 feet) dsmb. The size of the dsmb needed is really situational. In non current locals like Bonaire where I am shore diving thus shore is within swimming distance I should hope then a 3 feet long dsmb is entirely fine. For Cozumel, where despite boat diving mostly, I use a 4 feet long dsmb, I only send it up if I get off from the group. Florida east coast like Jupiter/WPB or some of the big wrecks down in the Keys I go bigger or additionally may carry a larger smb for inflation once on the surface should it be needed for better visibility. Still, I usually only put it up if I get separated or if the DM asks me too.

I put mine up at 30 feet. I use this depth because I do a safety pause there, I use the first part of the ascent to 30 feet to secure my camera rig. The mini spool has only about 40 to 60 feet of line. I hit 30 feet, my camera is now secured, I probably by now have the dsmb in my hands and unraveled and the bolt snap clipped off to a d-ring, then inflate and continue my ascent to safety stop depth and clip off the spool with the bolt snap.

There are several of the integrated dsmbs on the market now that have a built in spool pocket. These are usually around five or six feet of length. I am not smitten with them, I will be staying with a standard set up, three to six feet dsmb, spool, bolt snap and clipped off to my aft/butt d-ring.

Using the LP hose to inflate, a dsmb has an over pressure valve, just fill it up and let it go. For oral, it gets whatever I can get from my lungs and then I send it on the way. If it needs topped off on the surface so be it. Just saying, a fully inflated 3 or 4 feet dsmb is probably equally or more visible on the surface than a limp 5 or 6 feet dsmb.