Your SMB or DSMB is an essential piece of kit to help you be seen and found in the water. On the surface from a distance you are just a small head and shoulders, so a bright red sausage can make you more obvious in the water. SMBs and DSMBs come in a range of sizes, shapes and colours for different needs and they have a range of features to make your life easier.
An SMB or Surface Marker Buoy is a simple device that floats on the surface to mark a location. ‘SMB’ often refers to both permanent buoys and delayed buoys but they are made to mark a location in the water or communicate with the surface. Permanent SMBs are inflated at the beginning of the dive and you tow them with you on the dive so there is always a marker above you on the surface to mark your position so marine users stay clear. As SMBs stay on the surface they can be more intricate and include pockets for spares, small diver down flags and can be used as a floatation device if you get tired. SMBs tend to be round or torpedo shaped and often have a ballast section on the bottom with a weight or section that can be filled with water.
A DSMB is a Delayed Surface Marker Bouy that scuba divers take with them underwater. When you begin to ascend or if you need to contact the surface you can attach the DSMB to your reel and inflate it, it then ascends to the surface. When you start your ascent or at predetermined point in the dive, you send up your DSMB and hold onto it with line from your reel or spool so marine users in the area know you are there to either stay away or to come pick you up. After you have reached the surface keep it inflated so you are more visable.
Meanings change depending on where you are but these are the most common colours and meanings/reasons for using them.
Red SMBs are location markers, they mark a location in the water to return to or to avoid or tell marine users that there is a diver below about to ascend. Red is a good all-round colour that contrasts well with the water and can be seen far off.
Yellow SMBs are for emergencies in some circles but simple location markers elsewhere, you will often see EMERGENCY written down the length of a yellow DSMB and are used by advanced divers that cannot ascend to the surface but need help or equipment from the surface without surfacing.
Black SMBs are location markers like the red, black SMBs are said to contrast well against the water especially in bright conditions where the sun is behind you but they have sparked some debate and some skippers dislike them.
Multi-colour SMBs are also location markers, made to stand out more by creating a flashing effect as they turn on the surface so two-tone SMBs draw your eyes to be better seen.
Size and Shape
The size and shape depends on where you intend to dive, if you are in flat and calm waters a small DSMB can be enough to be seen so a compact DSMB can be best as they pack down small and do not weigh a lot. If you are diving in rough waters a large SMB can get you found faster and even in calm waters a large SMB will be easier to see. Round ones are better as static SMBs as torpedo buoys will glide through the water smoother.
Permanent SMBs just have simple valves that you blow up orally before the dive and close before you jump in. DSMBs have a range of inflation methods, the most basic of which is an open end that you exhale into or use your octo to fill to send it up to the surface. Open ended DSMBs are quite cheap to manufacture but you have to keep tension on the line as if they flop over on the surface the air inside can escape and the SMB sinks. You will often see fluted SMBs that are open ended but when inflated the opening is closed by the air pressure inside pinching it closed. Many DSMBs have a nozzle that has the same fitting as your BCD so all you have to do is push your BCD hose onto it to inflate the SMB and up it goes. Closed cell DSMBs often have this inflator and will stay inflated even if they flop over so they always stay inflated. The air you put into the DSMB will expand as it ascends closed and fluted DSMBs will have an over pressure valve that allows expanding air to escape so the DSMB does not explode but keeps them inflated and taught at the surface.
Some SMBs even have their own cylinders known as crack bottles that are filled up from your main cylinder before the dive and then inflate your DSMB by simply opening the valve. The small cylinder holds enough gas to inflate the DSMB and can be easier to use as you just have to open a valve and off it goes.
Reflective tape reflects light so shines back when a light is shone in its direction so you really stand out in the water especially at night.
Communication pockets are clear sections that you can roll a notebook page into to send a note to the surface or insert a glow stick to stand out on the surface, especially at night. Some DSMBs have bungees, velcro or pouches to store them in and wrap them up during the dive so they do not unravel.
All SMBs require some kind of line to hold it in position so it does not just float away. Most permanent and some DSMBs come with some line but you often have to buy a spool or reel separate. Good line management is essential and practice is the only way to improve. Rope and lines are dangerous in water and act very different to what you expect so take care and keep an eye on your lines.