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SMB vs DSMB what’s the difference?

Eric Larson   Jan 04, 2023

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Signal Marker Buoy (SMB) vs Delayed Signal Marker Buoy (DSMB) what’s the difference and do I need one?


In my Open Water training I know that marker buoys were talked about.  That said there was so much going on that I never really paid attention to that part.  When I started diving from boats, I would see them hanging up on a rack or in a bin for any of the divers to use.  That was all well and good but even though I understood the concept I had never touched one.  Shore diving was the only place where I had ever dragged a buoy, that was easy: flag, float & line. 


There are many applications for a SMB / DSMB and we’re going to go over just a few. These are the applications that are most common in our area with our types of diving.  Always check with your LDS & Dive Charter to what's common in your area.


1st lets talk about the difference.


Surface Marker Buoy (SMB) This is any device that lets people know that there are divers below and is towed for the duration of a dive. These can be in the form of a float and a flag, a colored tube that says, “Divers Below” or “Divers Down”. The tubes come in many colors but typically they are safety orange or bright yellow. The floats will have the dive flag on them.


Delayed Surface Marker Buoy (DSMB) These are typically connected to a line/reel and let people on the surface know that divers are starting to ascend and where they will surface.  These are brightly colored tubes (safety orange or bright yellow).  You can also get them with shapes on top like Nemo! (We have these in stock)


Many of these, except in the case of the Float & Flag, can be used interchangeably.  Let’s review the types of diving we do in our area, and which is appropriate.


Shore diving – In this case we are going to drag an SMB with us. This will alert people on the surface and more importantly boat traffic that there are divers below.  The most popular style for this is the flag, float & line.


Boat diving – I’ll be honest I don’t always jump in the water with my DSMB.  Sometimes when I have a camera, speargun, pole spear & stringer it’s not something I want hanging off me.  When the boat is tied into a wreck and there is little or no current, getting back to the line is not a challenge and therefore I have little concern over drifting off the line. If you dive off a boat that does not tie into a wreck, sometimes called “live boating” or “hot drops” you should always have a marker buoy with you and line commensurate with the depth of the dive.


Springs diving – Here it depends if you are at a place like Vortex Springs there’s no need for a marker buoy; the diving area is clearly marked and there’s no boat traffic. If you’re at a spring that is connected to a river or waterway, you’ll likely need to have a marker buoy.


Do you need one, yes! You should have one and more importantly you should know how to use it. Your SMB is straight forward, deploy enough line so the marker stays with you on the dive or blow up at the surface so you can be seen. Deploying a DSMB at depth is something that requires practice, your local dive shop can talk with you more about how to perform this skill.


Ask your local dive shop lots of questions, mention this blog in our shop and save %10 off your SMB/DSMB/Reel.


Remember to Have Fun!