What is an SMB?

Have you ever wondered what the big orange noodle is moving around on the surface of the water is?  Well, its called an SMB and I've written some useful information about it below...


SMB–Surface Marker Buoy

Surface maker buoys are one of the most important pieces of equipment we can carry as divers. In some countries they are required to use them before surfacing after a dive. However, a lot of new divers are not aware what a DSMB is or how to use them.


What is an SMB?

It is simple; an SMB shows the location of a diver on the surface and any water vehicles around the area, will need to go around them as the SMB shows that there are divers below. The area in which the inflatable device that floats on the surface of the water, can be seen from a boat or from the shoreline. They are especially useful when diving in a country where there is a lot of boat traffic. Often, they are coloured with a bright luminescent yellow or orange colour.


Differences between an SMB and DSMB?

Surface marker buoys (SMB) are brightly coloured buoys which show your position on the surface. They are made of thin rubber material and made for emergencies. Every diver should know how to use one. In some countries, it is required by the law to tow an SMB at the surface for your entire dive. This is usually in shallow coast dive sites where there is a high chance of boat traffic.

Delayed surface marker buoys (DSMB) are probably the most used option for divers. The ‘delayed’ part refers to the part that they can be send up during your dive, usually during your safety stop or when a problem occurs. When deploying your DSMB you will need to fill the tube partly with gas at depth to send it up to the surface. The DSMB will always be connected to a spool or reel.



The length of an DSMB varies quite a lot from less than 1 meter to more than 2.5 meters. Knowing this, you need to choose a DSMB that you can use and suits your type of diving. You need one that is long enough to be seen from a distance, but at the same time, it cannot take up too much space when rolled together for storage in the BCD pocket or drysuit pocket

Ways to inflate your DSMB

On open DSMB’s, where the bottom of the DSMB is kept open by a strong magnet, the most common way to fill the DSMB is by using your alternate air source. By clipping off your alternate air source and adding small amounts of gas into the tube you will see that your DSMB will slowly rise. As soon as your DSMB begins to pull, let go so it can reach the surface. Just a reminder, that this is not an appropriate method in cold water environments as there is a risk of a free flow from the regulator.

On closed DSMB’s there is a one-way oral inflation valve which allows you to add gas by blowing into it. By taking a breath, removing your regulator, and blowing into the oral inflation valve, you will blow into the inflator which adds gas to your DSMB. There is a high chance that you will have to do this twice. Some DSMBs will allow you to partially insert a Low-Pressure Inflator (LPI) into the valve to add gas quicker. When deploying DSMB from a deeper depth, you can take advantage of ‘Boyle’s Law’. As the DSMB ascends, the gas inside the DSMB will expand as pressure decreases and will become completely full of gas once it reaches the surface.


Are you interested in learning more about SMB and DSMB? Why not consider enrolling onto the PADI DSMB specialty. This course requires only 2 dives and can be performed in 1 day.

As a PADI Specialty and part of the adventures in diving program, this course will count towards your Master Scuba Diver rating. Let other divers know where you are with the PADI SMB Diver Speciality.

Written By: Jasper Mulder

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