With the latest update to the PADI Open Water Diver course, you were taught how to deploy a Surface Marker Buoy (SMB) on the surface.  But this does not really address the skill that you really need – how to deploy an SMB from depth.

When you deploy an DSMB from underwater – it is known as Delayed Surface Marker Buoys (DSMB). You will typically use these at the end of drift dives to let the boat know where you are. You may also use them in areas with boat traffic to make sure you are ascending safely.

Many DSMBs will have different features. The biggest feature that a DSMB can have is an over-pressure relief valve (OPV). The primary difference between a DSMB and safety sausage is that a DSMB will be deployed from depth. Whereas the safety sausage is deployed at the surface for signaling. As the DSMB rises from depth, the gas trapped inside will expand. As the gas expands it will stress the stitching that holds the DSMB together. If there isn’t some sort of mechanism to release this gas, then the expanding gas will rip apart the stitching of the SMB and releasing all of the gas, thus rendering the DSMB useless. 

Other features of DSMBs that are important are oral/power inflate and radar reflective tape. The inflation mechanism for DSMBs should be orally inflated or inflated with a drysuit/wing inflation hose. If the SMB does allow for LP hose inflation, there should not be a locking mechanism (like on BCD or dry suit inflation nipples) on the DSMB inflation nipple. This way if the DSMB quickly starts to ascend, it will not be locked to the diver causing a runaway ascent for the diver and the hose will just pull away from the inflation nipple. Radar reflective tape is also important. When the Coast Guard looks for lost divers in the water (both by boat and helicopter) they will have their radar going. Radar reflective tape is a piece of tape on the top of the SMB that will reflect a radar signal back to the source. Thus showing up on the Coast Guard’s radar screens. This will help the Coast Guard find the lost diver more quickly. Lastly, DSMB length is also important for surface visibility.  A 1.8meter long DSMB should provide enough surface visibility and  lift such that divers cannot easily pull it back down to depth.

Typical DSMB

When deploying a surface marker buoy from underwater, the air you put into it will change your buoyancy, so you want to be able to control your position in the water during the DSMB launch. Make sure that you don’t entangle yourself or another diver in your line.

As with many diving activities, deploying a DSMB is a team effort. At a minimum, there should be at least one SMB per dive team. It is a good rule of thumb for every diver to carry a DSMB in the event of buddy separation. The steps to deploy a DSMB as a team are below.

1) The dive leader will signal who should deploy the DSMB.  This is usually as you are preparing for a 5 meter safety stop.

2) The diver will signal to the team to watch them deploy the DSMB.

3) The diver shooting the DSMB will pull the DSMB and finger spool from their storage locations, often times the BCD pocket or clipped to the BCD.

4) If the spool isn’t already attached to the DSMB, the diver must attach it. Generally, most SMBs will have a small d-ring located on the bottom of them where the spool is attached.  The diver should un-spool the DSMB to make is easier to fill.

5) The diver should signal to a member of the team to look up to make sure that the SMB will not come into contact with another diver, boat, or other obstruction.

6) Once cleared to deploy, the diver should wrap up the spool, line and any excess DSMB material into one hand. Making sure that no materials, line, etc. are wrapped around fingers, dive gear, etc.

7) The diver should move into a slightly head down position. This makes recovering from a runaway DSMB much easier as the diver will need to swim down to control the DSMB.

8) Holding the DSMB and spool with the left hand, inflate the DSMB until about half full. If you are orally inflating the DSMB, take a normal breath, remove the regulator from your mouth with the right hand or hold the bottom of the DSMB up to the exhaust port of your regulator, blow a half breath into the DSMB, repeat until the DSMB is half full.  You will want to avoid taking to deep of a breath or exhaling to much as it will change your buoyancy. 

9) Once air is in the DSMB, hold the DSMB in the left hand and the finger spool in the right hand. 

10) Let go of the DSMB. As it rises, be careful as to not squeeze the finger spool to tightly. This could lead to a possible runaway ascent. The finger spool should gently unwind between the grasp of your fingers.

11) Once the DSMB reaches the surface, extra tension should be put on the line in order to make the DSMB stand straight up. To do this, wrap up the line on the finger spool 3 or 4 times.

12) You can lock the spool in place by removing the double ender snap from your right d-ring and clipping the line inside the double ender snap and through a hole in the spool. This will stop the line from unwinding from the spool.

As you move up the water column, you will need to wrap up the line on the spool till you get to the surface. Making sure you are keeping enough tension on the line to keep the DSMB standing up out of the water, but not to much tension such that you pull the DSMB back down. Due to the presence of line in the water, diver awareness must be heightened to prevent any entanglements with the line. Also keep in mind that the diver who is managing the line now has only one hand free to respond to problems, so team awareness and communication is critical.

Knowing how to deploy a DSMB is a critical skill for open water diving as this is a primary way to communicate with the boat/surface support. If you plan to do a lot of open water diving, including drift diving, your proficiency with this skill must be excellent.

-adapted from Precision Diving, Duane Johnson