HAVE YOU EVER WAITED at the surface, knowing that there are divers below you but not knowing where? That’s the predicament in which so many dive-boat skippers find themselves every day.
It’s nerve-wracking for them at times, and there’s always a sigh of relief when that familiar orange sausage-shaped balloon breaks the surface.
You, the diver, might think you know where you are, but in moving water you can cover a lot of distance horizontally between the bottom and the top, even if it doesn’t feel like it, ecause everything moves along with you at the same speed.
This is why the delayed surface-marker buoy or DSMB is so important and why, if you deploy one just as you’re about to ascend, or even at your last stop depth, it’s vital that you know how to do it efficiently.
Some dive-boat skippers tell me that they witness divers having problems deploying an SMB almost daily.
So how do you deploy such a buoy, as your dive draws to a close and the time comes to ascend.
You might choose to send it up on a long line from depth, if you’re about to leave the shelter of a wreck and subject yourself to the mercy of a current.
Or you might elect to do it from somewhere shallower, when you’ll need to be proficient at maintaining neutral buoyancy while you’re doing it.
When the time comes, the sausage-shaped buoy needs to be unrolled and attached to its line by a clip or karabiner, if it is not already attached.
The line is kept neat and ready for deployment in some way. Most commonly, it is deployed from a reel. Others favour a simple spool.
Some use a frame to wrap the line around, while others dispense with line altogether and use a length of narrow webbing 6-9m long, flaked into a bag with a small drop-weight at one end.
Whichever system you use, your aim is the same – to inflate the buoy from its open end as fully as possible before releasing it.
Once released, you want it to ascend directly to the surface while attached to a line that you are able to keep hold of, allowing it to pass through your hand without you getting dragged upwards with the ascending buoy.
To achieve this, first you need to be sure that the SMB is properly attached to the line. Push the empty buoy so that it floats above you. A tiny amount of air injected into it at this time will make it much easier to manage.
It‘s best to unwind a few metres of line from spool or reel, lock it and drop the line-dispenser below you. If you use webbing, pull it all out of the bag and drop it so that it dangles free. Webbing and drop-weights are best used from your last stop before the surface.
Now you have the opportunity to hold the open end of the buoy in one hand and fill it with gas from a convenient source.
I like to fill it using exhaled gas from my own regulator, keeping the reg in my mouth at all times but tilting my head so that the exhaust port is directed into the SMB. This means that I can have both hands free to hold the mouth of the buoy open.
I have big lungs, and it usually takes only around three exhaled breaths to do the job. If you are floating horizontally at this time, the line will be well away from your body, reducing any risk of it catching or entangling with your kit.
Some people prefer to fill using the purge of an octopus rig. This gives them the option to hold the buoy and line at arm’s length, with a similarly reduced chance of the line catching. However, one should be cautious about doing this in cold fresh water, in case the heavy flow of gas precipitates a free-flow.
Some people may use a gas supply from a regulator fitted to a tank other than the one from which they breathe.
There are aids available that can help, too. These are usually in the form of a funnel and are fixed to the reel, although this can make it bulky to carry.
If you fill the buoy quickly and decisively, you can get a lot of air into it before its buoyancy starts to take much effect. You can’t over-fill it – air that expands as it ascends is vented from its open end or over-pressure relief valve.
The safest way is to use an SMB with its own pre-filled (by you) mini-cylinder. Simply crack the cylinder and away it goes, filling from both the cylinder and expanding gas in the buoy on its way.
The line will pass rapidly through your hands, and drags the reel, frame or spool up to you. If you use a drop-weight and webbing, you should not use it at a depth greater than the predetermined length of the webbing.

THE LINE MUST BE ALLOWED to run freely through your hand, but you must also be able to grab hold of its dispenser securely when the time comes. Usually the buoy ascends faster than the spool can unwind without you holding it; the spool is soon raised back to your level.
I’ve seen divers in open water let a spool go by mistake, only to be pleasantly surprised when it drops, unravelling, back down to them – but don’t rely on this happening!
Obviously, you need to be able to unlock the line from the spool or reel when it reaches you. Many divers prefer to put a turn of line around the handle rather than use a lock release, if they don’t think they can rely on it.
Always use a buoy with a constriction at the filling end. This will avoid it falling over at the surface, releasing all its air and coming back down to meet you.
Some divers use a signalling system, with an orange buoy signifying that the dive is going as planned, and a yellow one signalling some kind of problem.
If you do this, be sure to prearrange your intentions with whoever is looking out for your buoy at the surface.
Lastly, never taken a reel for granted. Know exactly how it functions, and you won’t get caught out when it matters.

Use a buoy with a constriction at its filling end
Ensure that the buoy is properly attached to the line
Keep loose line away from your body and other equipment before inflating the buoy
Fill the buoy decisively before releasing it, and practise in benign conditions
Rewind the line neatly and evenly in the dry later.

Allow the line to become entangled in your equipment
Attach the reel to yourself or your other equipment before inflating the buoy
Get dragged up by an ascending buoy
Wind yourself up on the line while negatively buoyant
Forget to control your buoyancy by releasing gas from BC or drysuit during the ascent.