An SMB, or surface marker buoy, is a scuba diving accessory that no responsible diver should ever dive without.

It allows you to prominently mark your location in bodies of water, so that boats are aware of your location.

While it’s true that a dive charter or operation should always carry extra SMB with them, a self reliant diver should own one.

In this guide, I'll walk you through the different types of dSMBs, so you can buy the right one for your type of diving.

DSMB vs SMB: Key Differences

Shape, Color & Size

Why You Need a Reel with Your DSMB

While some SMBs come with wrapped lines, most divers prefer using a reel.

A reel safely stores the line, greatly reduces entanglement risk, and allows you to deploy your DSMB from depth.

Deploying from 15-20ft during your safety stop is the most common use case.

Carrying a longer reel is reccomended for deployment from a greater depth in the case of an emergency.

The simpler the reel mechanism, the less there is to go wrong.

A double-ended snap is used for attaching the DSMB to your gear and preventing the line from unraveling.

How To Inflate An SMB At The Surface

How To Inflate An SMB Underwater

Where to Store Your DSMB

Your DSMB should be easily accessible but secured so it doesn't drag or come undone.

Most divers clip their DSMB to a D-ring on their BCD using a double-ended bolt snap.

If you have a BCD with pockets, you can store a DSMB inside. For divers that use tech pants or shorts, they often come with pockets for storage, this is where I like to keep my SMB.

Do I Really Need My Own SMB?

Yes.

While your divemaster or guide should carry an SMB, relying on someone else's safety equipment is a bad habit.

I've been on plenty of dives where the group splits up, buddies get separated, or someone has to ascend early.

If you don't have your own DSMB, you're putting yourself at serious risk.

Losing the group isn't necessarily an emergency—but without a DSMB, you have no way to alert boat traffic as you surface. You're nearly invisible to the boat captain scanning the water for your marker.

Even if your buddy carries one, what if you lose your buddy too? It happens more often than you'd think, especially in poor visibility or strong current.

An DSMB costs $30-60 and weighs almost nothing. It clips to your BCD and you'll barely notice it's there.

Every diver should carry their own DSMB.

It's one of the cheapest, lightest pieces of safety equipment you can own, and it could save your life.

Which SMB Should You Get?

Mares Diver Marker Buoy

This is the DSMB I personally use. The 6ft (180cm) bright orange tube with reflective "Diver Below" writing and a 2-inch SOLAS reflective band makes you visible even in rough seas or low lighting.

It inflates quickly with 2-3 exhales or a short burst from your octopus, and rolls up small enough to clip to a D-ring without noticing it.