A delayed surface marker buoy, or DSMB, is an inflatable device that a diver deploys towards the end of a dive (during the safety stop) in order to make herself visible by boats at the surface.
As you can read in my post on Five Accessories Every Scuba Diver Should Have, the DSMB should be integral part of the equipment of every diver.
In this post I will cover the most important considerations you should make when purchasing a Delayed Surface Marker Buoy.
When buying a DSMB, important factors to look at are its color, size, and shape (open vs. close-ended). The DSMB shape determines the means by which you will be able to inflate it.
The final choice on which DSMB to buy depends purely on your diving profile and weather conditions during your dives.
We will be looking at DSMB colours, size, difference between technical and recreational DSMB.
1. DSMB Colour
Delayed Surface Marker Buoys are available in three main colors: orange, yellow, and pink.
You may find some variations with some brands producing slightly darker orange or shiny yellow. Some brands even produce bi-colored DSMBs, but there is not much to choose from when it comes to color variations.
The choice of DSMB color depends primarily on two factors. The type of dives you will be conducting and local diving regulations or usage.
For example if you will be diving during daylight from a boat, I suggest buying a regular orange DSMB. Orange is more visible by the boat crew.
If instead you will be diving mostly at night or in poor light conditions, a yellow DSMB is more appropriate. In fact, yellow is more identifiable at night (and better reflects the light).
In any case, if you are purchasing a DSMB for a specific trip, I recommend to get acquainted with local regulations. Alternatively, you can get in contact with the local dive center to ask for their preferences.
For example, in some locations (quite common in the UK), a yellow DSMB is used to signal distress. An orange DSMB is used to signal that everything is fine and that you are about to come out of the water.
Besides local regulations, there might be some rules specific to the dive center or boat you will be diving with.
Before you waste some money in purchasing a brand new DSMB, I therefore strongly recommend getting in touch with the local diving operator to make sure you are up to speed with local rules.
Given that DSMB color can be used for different communication purposes, I usually do not recommend buying bi-colored DSMBs.
Rather, I would suggest you buy two DSMBs with different colours (ideally one orange or pink and one yellow). This way you are sure you are prepared for any regulation or local usage.
2. DSMB Size
DSMBs come in different sizes ranging from 1 to 2.5 meters in length and have a varying width between 7 and 20 centimeters.
Choosing the right size depends pretty much on weather conditions during your dive. In a nice sunny day, with little to no wind and flat sea, a 1 meter orange DSMB will do perfectly fine.
In case of rough sea however, you might want to have a slightly longer DSMB in order to ensure that a dive boat or rescue operators will be able to see it while at the surface.
Consider that a 2 meter long DSMB will be easily seen also in case of 1 meter high waves. Hopefully if waves are higher that 1 meter you will not be diving as it can be quite dangerous.
Another consideration you should make when choosing the size of your DSMB concerns your level of expertise.
In fact, while deploying a DSMB seems quite an easy skill, it can turn to be quite dangerous if you are not well trained.
If it gets entangled to your BCD it can easily drag you to the surface generating a sudden ascent.
For this reason, for beginner divers, I usually recommend carrying smaller DSMBs that have a lower lifting capacity so as to reduce the risk of unwanted ascents.
3. Technical vs. Recreational DSMB
Another important consideration to make when choosing a DSMB, is whether you would like to buy a technical DSMB or a recreational one.
As you might expect, the choice is pretty much driven by your diving profile also in this case. If you will be doing mostly technical diving, then you will definitely want to purchase a technical DSMB.
If you will be doing mostly recreational diving you actually can choose your preferred option.
The main difference between a technical and a recreational DSMB is that a technical one is usually close ended, whereas a recreational one is open ended.
A close ended DSMB can be inflated either orally or with a LP hose connection via a special connector. And is deflated via a dump valve, just like the ones you have on your BCD.
An open ended DSMB, like the name suggests, is open on the bottom edge, so that it can be inflated either by purging air from your primary regulator (while keeping it in the mouth), or by using your emergency regulator.
Dumping of the air from an open ended DSMB is usually done by twisting it upside down.
For newly certified divers, I usually recommend buying an open ended DSMB as this is easier to operate and does not require you to remove your regulator from your mouth during a dive.
For more experienced divers the choice depends pretty much on personal preferences.
I for example, am more comfortable using technical DSMBs (i.e. close ended). Particularly those that are small enough to be inflated orally with a single blow.
Usually, recreational or open ended DSMBs also have more intuitive attachment systems. This makes it easier to connect them to your diving spool.
4. Best DSMB for different Dive Conditions
Wrapping up, choosing the right DSMB pretty much depends on the profile of your dives, weather conditions and on your level of experience as a diver.
Don’t forget to always check if there is some special color coding/signaling in your next diving destination.
As suggested earlier, if you buy two DSMBs of different colours you usually cannot go wrong.