As a scuba diver you may have been told how to use, used yourself or seen others use the DSMB.
Maybe some of you are wondering what it actually is and what it is good for, I will on the following page go in and describe how to use it and why it is in a lot of dive areas around the world, an important part of a divers equipment.
A DSMB is a buoy a diver can send up before surfacing after a dive, mostly being done on the safety stop. Sometimes it is necessary to send it up sometime before, like if you are on a drift dive you might want to send it up from depth, so the boat can see where you are and follow you until you surface.
How to send it up, well most of the DSMB's have a line with them that you can attach to the buoy itself, or you use a spool and attach it to the end. You there after take and hold on to the end of the line and the opening of the DSMB. Filling it up requires you to use air, here it is important to NOT use your own Second Stage regulator, this is YOUR air source and are not supposed to leave your mouth while under the surface. Instead take your alternative second stage (octopus) and carefully purge air into the DSMB.
This way you make sure that you can breathe while working with sending the DSMB up. Fill in air until the DSMB starts to pull upwards (around half of the DSMB filled with air) and then let go. The decreased pressure during ascent will expand the air inside and fill up the rest of the DSMB.
Another popular way to launch the DSMB is to tilt your head to the right and let your own exhaust bubble out into the opening of the DSMB.
So why is it so important to have a DSMB on you when diving in a lot of different areas in the world? First to begin with, you want to have a signal for the boat you are diving from, that you are on your way up and they can start getting closer to where you are so you can get picked up, saving some surface time in the water.
Second, you want to make a warning to other boats that you are surfacing in that area so they can keep a distance; there by reducing the risk of you getting hurt by propellers from other boats passing on the surface. They can't see you and will not in most cases see your bubbles.
Third, if you are drift diving and are in a strong current, you might want to make sure the boat can follow you and be ready to help you up after surfacing, so you don't drift away. This is a really good thing to do because you could risk getting separated from your dive boat in really strong currents and get dragged out to sea. So in this case it is a good safety marker to have on drift dives.
I have a DSMB, not only because it is required of me to do my job as an Instructor/ Dive guide, but also because I work in an area with a lot of boat traffic every day around the different dive site we visit. So I use it to make sure, that the boat can see me coming up from a dive with my customers, and avoid accidents. Boats in my area is mostly good in keeping a distance from the buoys, I guess it is because of they know a lot of divers are in the water.