Using an SMB


What is an SMB?

An SMB is used by divers, with a line and reel, to indicate the diver’s position to their  boat while the diver is on the safety stop (decompression stop) or on their way to ascent. It is otherwise known as a surface marker buoy

Some divers drag a buoy (usually a little bigger than an SMB) during their dive so the boat can see the divers position at all times.  This reduces the risk of losing contact when air, light or sea conditions decrease the visibility of the divers from the boat.

Here in Costa Rica we use the SMB once we are ascending from a dive without a descent/ascent line. We currently have about 4 sites that are marked this way but many more that aren’t. So the SMB’s for us are very handy. They signal where you are, not only for your boat but also for any passing boat traffic that there might be. Another good use for it is to signal your location at the end of a drift dive when you could end up far away from the boat.

The sausage is a plastic tube that is normally inflated by putting one end under water and purging the second stage underneath to inflate it. Inflated tubes are normally about 6 feet (2 m) tall. Un-inflated sausages roll up and fit in a bcd pocket or you can clip it to your jacket along with the reel that you need to send the SMB to the surface. Commercial boat dive operations, especially at offshore reefs or areas known for strong currents or mercurial weather, may require divers to carry safety sausages. A safety sausage is not a substitute for a surface marker buoy or diver down below flag. They are also not intended to be used to lift items, for this you would need a proper lift bag.


Deployment problems

Several common problems are encountered when deploying your SMB

  • The reel jams after the buoy is inflated (dragging the diver up). To avoid this, a diver can:
    • use a simpler system or a reel which cannot jam (e.g. a weighted spool);
    • detach the lanyard connecting the diver to the reel before inflating the buoy (and ensure no equipment is trapped in the buoy or reel);
    • attach two reels to each other in series. If one fails the other is unlocked to reel out its line.
  • The diver removes the primary air source from his or her mouth to inflate the buoy, and is therefore at a disadvantage in dealing with any other problems that might arise as the SMB goes up. The ways to avoid this include:
    • using a secondary demand valve, such as an octopus, to inflate the buoy;
    • using a sealed buoy with an inflation valve, which is filled by blowing directly into the valve inlet or by attaching a medium-pressure inflation hose from the BCD  (the valve does not retain the hose connector, like the BCD  and the hose can be easily pulled off the valve
    • Make sure the SMB is tightly attached to the reel and check before every dive
  • The SMB is not attached properly, and once inflated, shoots to the surface and diver might lose the SMB:
    • Make sure the SMB is tightly attached to the reel and check before every dive

PADI has an SMB specialty and we will be making this a mandatory course for all dive master’s in training starting next season. We are noticing too many divers not being familiar with the SMB, even though it is part of the advanced diver course.  If you sign up for a PADI Advanced Open water course with Rich Coast Diving you will have included in your pack a really nice “PADI” branded SMB, which will be yours to keep 🙂padi smb


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