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Choosing and using the right dSMB for you!

The latest piece of kit we are going to put under the spotlight in this blog is the humble dSMB.  This is one piece of kit every diver should carry and could end up saving your life. Having said that, many people still don’t actually know what a dSMB is and / or does!

Deploying a dSMB from underwater.
Deploying a dSMB from underwater.



A dSMB (or Delayed Surface Marker Buoy to use its full name) does exactly what it says on the tin.  It is a signalling device to alert boats and other motor vessels above the water that there are divers below.  It is generally put up towards the end or at the end of a dive, when the divers underneath are getting closer to the surface.


In more extreme cases they can also be used by technical divers to alert the surface team that a diver below is in distress.


They can also be used when at the surface to attract the attention of the boat if it is far away or in choppy waters


It is now part of the new standards of the Open Water course that PADI have produced, that every student should know how to deploy a dSMB.




So now we know what one does, and how important they are, what should we look out for when we make this investment?


dSMBs should be bright in colour (usually orange), and large enough when inflated so that they can be clearly seen from the surface by motor vessels even in high swells.  Usually they have the caption ‘diver below’ or something similar written down the side.

Yellow ones should be reserved for technical diving as these indicate diver distress, and that the diver needs help, and usually have writing saying as much on them.


dSMBs are made in 2 main types of materials: the cheaper ones are usually made of plastic, while the more expensive ones are some sort of hard wearing nylon material.   The cheaper ones do tend to slpit at the sides when used a lot.  A good quality material one may sound quite expensive, but will last you a l0ot longer and be more cost effective in the long term.


Another consideration is whether you want a dump vale to let the over flow of air out on the way up.  This is a much more controlled way to vent the excess air and leaves you with a full buoy at the surface.  The other type is open ended at the bottom to allow the expanding air out, but more often leads to too much air being released which means a rather floppy, sorry looking buoy at the surface!


Finger reel
Ratchet reel


There is also the question of how you want to deploy your marker buoy.  You have 3 different options and these really do come down to personal prefence.  The most common two types are the reels.  First is the finger reel, which are smaller and easier to carry around, but can be more prone ton tangling.   The second is the ratchet reel, which comes with a handle and ‘stopper’.  These are much bulkier, however and are not very travel friendly!

dSMB tape


Third is using a tape or string.  The downside to this is that they are normally only 5m in length, so you can’t deploy your dSMB from any deeper than that.  Also it means that unless you are very conscientious, you will most likely have tape dangling about underneath you which can be a real entanglement hazard for you and those around you.







The way in which you inflate your dSMB is another consideration.  You can use your alternate air source (most common), just at the entrance of the inflation end and purge the

Gas canister for dSMB deployment

mouthpiece.  (Don’t forget to let go!!)  Some smaller dSMBs may oral inflating, but these tend to be more like back-up ones.


There is one more way to inflate your dSMB, if you are into your gadgets, and that is with a cannister.  This is filled directly from your air tank and attached onto the dSMB.  Then when you want to deploy it, you simply turn the handle, and up it goes!  Not the most lightweight, travel friendly design, but certainly very effective!!






Whichever type of dSMB you chose as your preferred method of choice, it really doesn’t matter.  The important thing is that you learn how to use it properly, and you should take it with you on every single dive.  You never know it could just save your life!

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