To us divers one of the most important thing is being seen at the surface. It might be from our surface cover or other dive charters in the area. During open water decompression away from a mooring line this becomes even more important. There are two stages during this that you are the most vulnerable at. The first situation is at your shallowest stop, usually 3-meters or when you actually are on the surface.
A DSMB would make this diver more visible to the boat
One of the tools available is a DSMB, a delayed surface marker buoy. This is the kind that you would deploy during your ascent to make sure that people on the surface are aware of the fact that you are about to surface. If there is a current the surface cover will have a much easier job following your marker then just your exhaled bubbles. A DSMB is usually red or orange. Typical length is one meter but for dives in rough sea, a two-meter marker might be a better investment. The tall cylindrical shape of the marker is favorable over the lift bag since not only does it stand out of the water taller but it also creates less drag due to it’s decreased surface area.
All DSMB´s should be attached to a finger spool. A 100-feet spool is more then enough. I usually shorten the line by a few meters to make the holes in the spool more accessible. At the end of the line a loop big enough for the spool to fit through with a much smaller loop at the end will make it easier to deploy. Some prefer to have the marker attached to the spool during the dive whilst some prefer to keep them separate and connect them when it’s time to deploy the marker.
There are some different options to inflate a DSMB depending on what type is being used. The cheaper ones will be open at the bottom end and the way to deploy them is by tilting your head to the right and letting your exhaled bubbles enter the marker. Some divers use their alternate air source to inflate the bag but this is something I would avoid due to the increased possibility of entanglement. These markers can spill out some air upon their ascent, to prevent this some tension must be kept on the line at all time.
Some markers have a self-sealing deign at the bottom which present air to escape, to prevent rupture from over filling, this design is used in conjunction with a overpressure valve.
The last one is the sealed marker. This is the one that I currently use and it is in my opinion the best design. To inflate these markers a slightly different method
DSMB with the divers initials
is used. They have an inflator with a one way valve which you would seal your lips around and exhale. No gas is spilled and it is very easy to get the marker fully inflated every time. Some inflators have the option to use together with your LPI hose. Detach your LPI hose from your wing or drysuit and connect it to the marker, since the male end of the connection does not have the “groove” typically found on the inflator head of a wing the hose wont get stuck on the marker so there is no risk of getting dragged to the surface with it. For CCR divers this is the preferred method of use but this also applies for coldwater diving. Your lips are usually the first to go numb and it is nearly impossible to seal them around the inflator after a long dive.