SMB vs. DSMB: What's the Difference and Do I Need One?

In my Open Water training I know marker buoys were talked about — but there was so much going on that I never really paid attention to that part. When I started diving from boats, I'd see them on a rack for divers to use, and even though I understood the concept, I had never touched one.

Surface Marker Buoy (SMB)

Any device towed for the whole dive that lets people know divers are below: a float and flag, or a brightly colored tube (usually safety orange or yellow) that says “Divers Below.”

Delayed Surface Marker Buoy (DSMB)

Usually connected to a line and reel, deployed from depth to show people on the surface that divers are ascending and where they'll come up.

Which one for which dive?

• Shore diving — drag an SMB the whole dive to alert boat traffic. Flag, float & line is the most popular.
• Boat diving — when the boat is tied into a wreck with little current, getting back to the line is easy. If the boat “live boats” or does hot drops, always carry a marker buoy with line suited to the depth.
• Springs diving — at a marked site like Vortex Springs there's no need; at a spring connected to a river or waterway, you likely do.

Do you need one?

Yes! You should have one — and more importantly, know how to use it. Deploying a DSMB at depth takes practice; ask us and we'll help you work on the skill.