DSMB’s, or Delayed Surface Marker Buoys, are a diver’s best friend. Used for communication with surface crews or boats while the diver is still at depth.
They can be used to signal the need for a boat pick up, as a distress signal, a marker of a location (maybe of that sunken treasure you found?), or to indicate the need for additional air on long decompression stops.
Basically, they are tubular buoys made out of PVC or similar materials, and attached to a line reel or spool. They are typically orange, red, or yellow, sometimes with various colors used to communicate various messages.
Here's more about SMB And DSMB: Identifying Your Marker Buoys.
At many dive spots you'll see them vary in colors and manly be used to signal for passing boats, before divers accent.
It's one of those safety items commonly used, and often required, during boat or drift dives, where they are used to signal a diver’s or dive team’s position as they surface, and are typically launched during the safety stop.
Launching one can be a bit tricky, though, as they influence your buoyancy, but also due to the risk of getting tangled up in the line and getting pulled to the surface by the DSMB. This guide will teach you the basic steps to launching a DSMB safely.
Setup of a DSMB
First things first, setting up your DSMB. I recommend attaching your DSMB to a spool, rather than a line reel.
The reason for this is two-fold: First, the spool is lighter and smaller, meaning the whole setup takes up less space in your configuration. Second, a line reel will have some form of locking mechanism that can potentially jam, sending you the surface if it jams as you launch the DSMB.
For a step-by-step guide to how to put together a DSMB and line spool, here is a great video tutorial:
Once your DSMB is setup, store it in a BCD pocket, or simply clip it to your BCD.
Deployment during SCUBA diving
When it comes time to launch it, here’s a step-by-step guide:
- 1As DSMB’s are often launched during safety stops, that means you most likely need to launch it mid-water, so make sure your buoyancy skills are up to spec. When it’s time to launch, find your perfect hover point, and expel a small amount of air making yourself just a tad negative in the water.
- Take out the DSMB and unpack it, taking care not to drop the reel. As it has no lock it will run out its full length of line before stopping, which will be a mess to coil up again once you’re out of the water.
- Holding the DSMB and line spool in your left hand, use your right hand to pull open the bottom of the DSMB.
- Tilt your head slight, bringing one of your regulator exhaust valves close to the opening of the DSMB, taking care not to get the line entangled with your regulator or regulator hose.
- Take a moderately deep breath, hold the opening of the DSMB over the valve, and exhale. Your exhalation gas will run from the exhaust valve and into the DSMB.
- Repeat this once or twice as needed, until you feel a strong tug from the DSMB (use your breathing to counter the positive buoyancy of the DSMB or release a small amount of air from your BSC), then release it, holding the line spool between your right and left index fingers and allowing it to un-reel line as needed.
Once the DSMB breaks the surface, reel in a bit of line so it is taught and the DSMB stands straight up on the surface, making it as tall and visible as possible.
Remember to check your depth and dive computer from time to time. Rather take a minute longer deploying your DSMB than you accidentally pop to the surface.
Training in the Deploying
Many divers will tell you to use your alternate second stage to fill the DSMB, but there are several advantages to the method described above, where you use your exhalation air instead.
First, filling air into a DSMB makes it positively buoyant. By using your exhaled air, there’s no shift on your overall buoyancy. Second, this method allows you to fill your DSMB even if you’re diving with a technical setup, where your secondary second stage is stored in a necklace around your neck.
Practice makes perfect, of course, so make sure you practice this before needing to do it for real, and keep practicing from time to time to keep your skills honed.
A pool or a local dive site is perfect for this. But make sure to let any shore based bystanders know that you’re only training, so they don’t misinterpret it as a distress signal and start calling the coast guard.
Do you use a DSMB when diving? In what situations do you bring your DSMB? Tell us in a comment below!