Delayed / Surface Marker Buoy (SMB/DSMB) – Selection & Deployment

SMB at surface

Deploying a surface marker buoy is critical in many parts of the world for diving and now it is required as part of the PADI Open Water Diver course.  We definitely agree that is a must know skill for divers. We have been part of a few rescues where improper DSMB deployment use or inadequate SMB size caused divers not to be noticed by the boat for pickup.  NO diver wants to be left in the water.  I will use the terms SMB and DSMB interchangeably, just understand the only difference is DSMB would be deployed underwater after dive start, usually on ascent (delayed); SMB would normally be deployed on the surface at the beginning of the dive.  The skill that I will be talking about is deploying the SMB underwater.

Very recently we were on a dive where another buddy team suffered from two mistakes:

  1. They had an inadequately sized DSMB
  2. They lost control of their DSMB

A critical task is to conduct pre-dive checks.  Pre-dive checks are not simply making sure you have equipment, they are there so that you make sure you have the right equipment.  The right equipment will vary depending on many factors … basically your decisions should be made in the following manner:

  • What is the Dive Goal
  • Surface/Water Conditions
  • Dive Site Location
  • Buddies/Equipment Available
  • Time
  • Environmental Impact Considerations

Going back to choosing proper SMB size, if we were diving in the Philippines and it was super flat, clear waters then perhaps a 1 meter SMB could be appropriate.  Now lets move to the Korean East Coast.  On the East Coast conditions can change throughout the day at a moderate pace, also we have seen currents pop up out of no where once in a while.  On the surface there are generally some swells that range from small to fairly large (we dive in all types of weather so long as the boats are allowed to leave the harbor with our experienced divers).  Even with small swells a small DSMB is difficult to see from a distance in this environment.  Most of our divers opt for the larger 1.6 – 2m tall DSMBs.  For South Korea we personally feel that these are the bare minimum for our environment.

This is a video of the tail end of a 2.5+ hour search and rescue where divers were diving with too small of an SMB and they lost control of the SMB as well. Needless to say we were all very grateful when we located the divers.

Now let’s talk about deployment of your DSMB.  This task execution must also be carefully evaluated based on environment.  Many instructors teach students to use their alternate air source to put air into the SMB.  This is a technique but not an ideal technique.  Why not?  If you dive in Korea the water temps in deep water (or in winter months) can reach 5º C.  With water temperatures that cold there is a high probability that your alternate air source will freeze causing a free flow.  Now you have two problems to deal with, (1) you probably just overfilled your SMB and it is out of control (unless you are experienced with SMBs) and (2) you now have a free-flowing regulator wasting precious breathing gas.  Neither are good and the combination probably caused the less experienced diver to also lose control of the SMB reel, so now that is gone.

So what is the right way to deploy an SMB?  There is no 1 specific right way, it is all dependent on your surroundings, however there are ways that work in most situations.  There are 3 techniques that work well in all environments:

  1. Fill your SMB with your exhaled breaths directly from regulator to bag
  2. Fill your SMB by blowing into the oral/power inflator nozzle
  3. Attach an extra low pressure inflator hose to your 1st stage that you will use to inflate the power inflator nozzle.  The same style hose that attached to your LPI (low pressure inflator) on your BCD.

We found 3 good videos on YouTube that showcase each of the options. These are not our videos and we are not affiliated with any of the owners/instructors etc.

Option 1 does take practice in maintaining proper buoyancy and trim however one plus is that the regulator never comes out of the divers mouth.  This however will NOT work for CCR divers, as we simply don’t exhale into the water.  Alternate air source freezing won’t occur.

Option 2 does require the diver to remove the regulator from his/her mouth and blow into the oral/power inflator nozzle.  This could require multiple breaths depending on depth and amount per breath the nozzle allows to pass through.  There is very little chance that too much air will rapidly enter the SMB as the diver controls each amount with precision. Alternate air source freezing won’t occur.  This again would not be ideal for CCR divers as they would deplete their loop contents and change the loop mix.

Option 3 would work for all divers (OC and CCR).  Simply connect the LP hose up to the power inflator nozzle and carefully fill.  Alternate air source freezing won’t occur and the regulator always remains in the divers mouth.

We understand there are several other variations out there that would work as well, such as using the existing LP hose attached to a diver’s low LPI however anytime a diver disconnects items there is a possibility of failure or inability to reconnect.  Each diver must carefully conduct a personal assessment on which way to setup his/her gear and task execution.

Finally a last note, make sure you can find, reach and fluidly deploy your SMB. This is where practice comes in. Start by testing out configurations on dry land in our home. Then do it blindfolded. Then move to the pool. Slightly adjust locations and setup until you find one that works best for you without violating the above consideration list. Think safety first at all times. Finally when you have mastered the skill in the pool move to the ocean. With the help of buddies record each others’ deployment of DSMBs to see how you really look executing the task.

As always if you have any questions please don’t hesitate to contact us and keep your eyes peeled for our next dive clinic.  Not sure where to pick up an SMB like ones that we mentioned above?  Comment below or PM us on Facebook

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