Difference between SMB & DSMB

[Yeoh Chee Weng]

I just read about the 12 missing divers in the Red Sea incident and a DSMB was mentioned. What does DSMB stand for? Is there a difference in the make of a DSMB with that of an SMB and when do you deploy the DSMB? I've done my PADI course up to Rescue Diver and deployment is not taught, perhaps when you opt to do Search & Rescue specialty? If SMBs are such an important safety measure why does not PADI include it as compulsory? Most divers, including myself learn on our own by trial & error and I have come across divers who found out that the "sausages" they bought collapsed soon after they ascended making them useless for alerting boat pickup should they drift too far from the entry point.

 

[vjongene]

I just read about the 12 missing divers in the Red Sea incident and a DSMB was mentioned. What does DSMB stand for? Is there a difference in the make of a DSMB with that of an SMB and when do you deploy the DSMB? I've done my PADI course up to Rescue Diver and deployment is not taught, perhaps when you opt to do Search & Rescue specialty? If SMBs are such an important safety measure why does not PADI include it as compulsory? Most divers, including myself learn on our own by trial & error and I have come across divers who found out that the "sausages" they bought collapsed soon after they ascended making them useless for alerting boat pickup should they drift too far from the entry point.

SMB = Surface Marker Buoy; DSMB = Delayed Surface Marker Buoy. Have a look at this picture.

The difference is that a DSMB is always tied to a line, and deployed from depth, while an SMB may be deployed from the surface only. Basically, add some line to an SMB and it becomes a DSMB, so there is no basic difference. (D)SMBs can be open at the bottom, or closed with a valve. When inflated, they stick out at the surface, thus marking the position of the diver. If deployed from depth, they normally contain enough air (expanded by the travel to the surface) to be well inflated. It can be trickier to get enough air into an SMB at the surface, especially the open type.

The is a special forum on ScubaBoard dedicated to SMBs. Look under the Equipment section.

The use of SMBs is AFAIK not covered in any of the basic PADI courses. In our CMAS curriculum, we cover it at the two star (Rescue) level, but it is not a mandatory skill. I believe that it is covered in the BSAC curriculum, because the diving conditions in Britain (boat diving and strong tides / currents) make them essential for safety. Many people recommend the deployment of a DSMB as soon as a dive becomes a drift dive. Also, it is common practice to deploy one during deco or safety stops, so that the boat will know where you are.

A lot more could be said. Hope this answers some of your questions.

 

[String]

As mentioned, SMBs tend to be bigger, rounder and inflated on the surface and towed on the dive - ie a parmanent marker, i think americans have something similar and call it a "dive float" (?).

Delayed SMBs are intended to be deployed from depth, tend to be maybe 5-6ft long and sausage shaped. You can have open ended, sealed and even self inflating ones.

Both acheive the same goal, allowing the surface traffic to know where you are.

If going on a drift dive typically an SMB is the best choice although these days lots of people, myself included just own a DSMB and inflate that on the surface before descending as it does the same job.

In the UK and other areas with big currents, roughish seas and low visibility nearly all diving is what some people call "live boating", in other words boats dont anchor and you dont go up/down the anchor line. You often go down a shot line but rarely come back to it, at the end of the dive before starting ascent you release a delayed SMB and surface underneath that meaning the boat cover can follow you and know where you are.

Standard procedure here also is if you leave the wreck or the current starts running you immediately deploy a DSMB and tow it throughout the remainder of the dive so the boat traffic can follow you.

AIK not covered in any of the basic PADI courses. In our CMAS curriculum, we cover it at the two star (Rescue) level, but it is not a mandatory skill. I believe that it is covered in the BSAC curriculum, because the diving conditions in Britain (boat diving and strong tides / currents) make them essential for safety.

BSAC both are taught in theory at sport diver (2* / second level qualifcation) however in reality you'll probably find no club will let you in the water at any level without the knowledge and as a result even novices are trained in their use and required to own a delayed buoy and reel before they qualify for even basic qualification.
Example with me, on my first ever dive i inflated instructors DSMB with my octopus, on dive 2 he inflated and i released the reel. Dive 3 i was reeling up. It continues from there and this is normal.

In conditions we get here a DSMB is a vital safety aid and IMHO (and others) really should be compulsory for the basic level training.

 

[Yeoh Chee Weng]

Thank you, now I understand. Here in Malaysian tropical waters where we drift dive I've yet to see a divemaster or anyone deploy a DSMB and drag it along the surface. At the end of the dive a "sausage" is deployed. The boat crew, I guess, is alert enough or he knows the current so well that he can follow us without fail. However, now that I know better, if I'm separated from the rest in a drift dive I'll deploy my DSMB and drag it along with the flow of the current.

 

[String]

Bubble following isnt terribly effective in 6ft+ seas even if you do know the current