shutterstock 146826473 opt

Easy Diving | SMBs

 Knowing how to deploy an SMB is a basic skill all divers should know

A surface marker buoy (SMB), or more correctly a delayed surface marker buoy (DSMB), is what many divers will know as a balloon or ‘safety sausage’. For recreational divers, on a holiday dive, it’s the orange blob the dive guide shoots up to the surface towards the end of the dive, meaning the safety stop and final few moments of the dive are at hand. Some people carry them, perfectly packaged and never used because they were sold these items as essential dive safety equipment, yet have no idea how to use them, or even what they’re for. But the guide’s got one, so that’s okay, isn’t it?

Er, actually, no. It’s not. An SMB is one of the most essential pieces of safety equipment you can possibly carry. There are situations where relying on someone else to deploy one puts your life at risk. Imagine, for example, that you’re drift diving and the current picks up strongly and unexpectedly, bringing with it a serious reduction in visibility and pushing you away from the reef, out to sea. You turn around and can’t see your guide any more, or your dive team, or even your buddy. You surface in a rolling 2m-high swell beyond the end of the reef. It’s late afternoon, the tropical sun is halfway to the horizon behind you and the sea is a gloriously shimmering blaze of fire-bright orange. Your captain is blinded and – more importantly – looking in the other direction, because you were supposed to surface somewhere else. It’s going to be incredibly difficult to be seen, or catch anyone’s attention.

It happens, and sometimes situations such as these are beyond anybody’s control, even with the best planning in the world. Every now and then, it all goes pear-shaped. 

Firstly, let’s clear up the acronyms. An SMB is a buoy at the surface that marks a location. This doesn’t actually have to be you – it could be anything. In some locations, you’re required to tow a marker flag or SMB for the entire dive. 

So we use the term DSMB, specifically to mean a marker buoy that is sent to the surface at some point after the dive commences. It’s usually deployed towards the end of a dive, to indicate the position where the team will surface so the captain of the dive boat has advance warning. Unless he’s asleep at the wheel (again), which happens.

A DSMB can give your boat cover advance warning if you are drifting out of position and into harm’s way. There are many reefs where the current can drag you into dark and dangerous waters – letting your crew know you’re heading in that direction may well avert disaster. There are a number of unfortunate stories of divers being left behind or drifting through the ocean for several hours – or days. Some method of communicating at a distance is essential to a diver’s safety.

There are different types of DSMB, and they’re not necessarily either good, or inexpensive. I’ve possessed several types during my career and due to lack of availability or personal finances, have owned both an overpriced piece of plastic pants and a most excellently versatile and inexpensive sausage of perfect poise. I’m not going to name any manufacturers, but the plastic pants people please take note: I’m going to hound you to hell and back until you start making useful, practical, robust pieces of equipment that are not ridiculously overpriced. £100 for a balloon? You’re kidding, right?

Your SMB should be at least one metre long when fully inflated, anything more is a bonus. The open-ended non-return valve is a simple piece of engineering: it’s just a couple of flaps that allow you to inflate your SMB using an alternate air source and the expanding air seals the valve closed to stop air leaking out and too much water getting in. The magnetic weights help keep the seal closed and also pull the balloon slightly so it stands – er – more erect. The dump valve allows you to deflate the SMB easily, both underwater and at the surface, and also stops it exploding thanks to the non-return valve. The low pressure inflator/oral inflator mechanism is a wonderful thing, because it gives you a number of different options as to how you can inflate your balloon (I will come to these in a moment).

So should you use reels or bits of rope? Reels please! They don’t have to be super-reels – a decent finger-reel with 20 metres of line and a double-ended clip should set you back about £10 and does the job well. The problem with SMBs that have lines attached is that these lines can’t be very long. Usually between 5 – 7 metres. This has the major disadvantage that the SMB can only be inflated at or around safety stop depth, which is not much use if you’re deeper. Secondly, you have to unravel all that rope which is left to float around in the current until you send up the balloon – a major entanglement hazard. For two years I carried an SMB with a six-metre line and even though I was using it every day, I still managed to get tangled in it once or twice. I’ve even seen lines become so entangled that sending up the SMB has yanked the regulator from the diver’s mouth.

shutterstock 64318156 opt

A reel is more straightforward to use. There’s lower risk of entanglement and the sausage can be shot up from greater depths. I usually inflate mine at around 10m, which gives ample time in case someone fails to stop at 5m for their safety stop and accidentally floats to the surface. It gives my captain a little bit of extra time to wake up, stow the newspaper, fire up the engines and come and find me. Finger reels are ideal for most conditions. Hold it on the middle finger of your left hand if you’re right-handed (and vice versa if you’re a lefty). It leaves your other fingers free to hold the SMB and your right hand (or vice versa) to operate the alternate air source, should this be your chosen method of inflation. If it is, dump the air from your BCD and breathe out as you inflate (takes a bit of practice). Give it a good shot from the purge button and – this is the important bit – let the balloon go. It doesn’t take much to inflate and remember, from 10m, the SMB only has to be half-full to be completely full at the surface.

Which brings me to my next point about the oral inflator. Some models of SMB have a plastic tube which connects to a low pressure inflator hose from your regulator, but also doesn’t lock in place. You can quickly disconnect your BCD or drysuit (or use the spare if you have one), and use this to inflate the balloon. My personal preference, however, is to use this same device to orally inflate my SMB. This has one distinct disadvantage in that you have to remove your primary regulator to do it. However the major advantage is that you maintain neutral buoyancy. The air from your lungs is going into the balloon which means the system as a whole – in your lungs, BCD and SMB – maintain the same buoyancy throughout the procedure. If you inflate by any other method then you are adding several extra kilos of positive buoyancy to the system, hence a tendency to rise up. Orally inflating your SMB will increase your buoyancy a little bit since the expanding air in a tube one metre or so above you will inevitably pull you to the surface, but it’s much slower and much more controllable than trying to inflate with an alternate air source. Take a deep breath, remove the regulator, hold it in your hand, use the available fingers on your other hand to bring the inflator to your mouth, breath deeply into the SMB, let go of the balloon, rise and shine!

Wind yourself up to safety stop depth, and clip the line to the holes in the reel so the line is locked in place at 5m. Be wary of passing dive boats, speedboats, glass-bottom boats, boats towing daft inflatable bananas, jet-skis, strong surface currents, tubby Russian snorkelers and curious sharks (all true) and wind yourself up to the surface. If you need to deploy your SMB because you get lost on a night dive, try shining your torch inside your long orange sausage – now you have a glowing metre-and-a-half of signal light that can be seen for miles. You can also use it to have Jedi-style lightsabre battles while you wait for the boat captain to wake up and come and find you.

While we’re on the subject of being picked up, it’s really a good idea to tell the captain of your boat, or your shore-based support station, where you’re going and where you might finish when it all goes according to plan. Or where you might end up if it doesn’t. Hopefully somebody will eventually look in your direction. If they don’t, I would recommend you start blasting out with the whistle you carry attached to your BCD shoulder. You do carry a whistle, don’t you? No…?


- Carry an SMB. They really could save your life one day

- Invest in a reel and some clips. It doesn’t have to be fancy, it just has to be a reel and some clips.

- Practice in super-easy conditions. A lot. Trying to use an SMB for the first time after it has all gone pear-shaped is not advised!

- Buy an orange or red one. Yellow SMBs look a bit dull.



- Leave home without one



Love diving? You'll love these. Sign up today to immediately download our unique FREE gifts -

AROUND THE WORLD IN 80 WRECKS - DIVE's 70-page, beautifully illustrated, colour guide to the world’s best wrecks

SCUBA STORIES - DIVE's collection f real life stories where divers, who have got themselves into perilous situations, describe how they reacted and what actions they took to ensure they lived to tell the tale

PACIFICHighlights of the Pacific - Dancing mantas in Hawaii • The Best Diving in the World, Galápagos, Cocos, Malpelo & Socorro • Mass Spawning Events in Palau

New Upright Gift Banners 300 x 600 px

Sidebar SUBSCRIBE spring 21 large2

Destinations Spotlight

Need inspiration for your next dive trip? Try one of our featured destinations from DIVE's travel partners.

sidebar philippines sidebar bahamas sidebar mexico sidebar fiji sidebar st helena 2020 Sidebar Egypt sidebar banner sabah sidebar banner belize sidebar banner south africa

DIVE Partners

sidebar banner egypt new ceningan divers ad 300x100 LH 300 min giphy subex Wakatobi Siladen Aggressor Fisheye Dive Worldwide gozo banner Arenui

Read DIVE magazine

DIVE magazine is available to read on many devices. Simply click one one of the options below

PCMac final
Apple finalAndroid final

Like what you see?

Join us on social and keep updated daily...