Surface Marker Buoys: What You Need to Know

Not All SMBs Are Created Equal

This guide is specifically about dSMBs (delayed Surface Marker Buoys)—the kind you send up from depth before surfacing. For why you should carry one and how SMBs fit into your overall safety strategy, read Surface Marker Buoy: What It Is & Why You Need One.

Choosing the Right dSMB for Your Dive Style

There is no universal dSMB. The right choice depends on your environment, dive objective, and gear setup.

Dive Type	Recommended dSMB
Recreational Boat Dive	4 to 6 foot closed-end with oral one-way valve
Drift Dive	Large (5 to 7 foot), bright orange or yellow
Low Vis / Night Dive	dSMB with reflective tape or strobe attachment point

Color note: Orange and yellow are most common. Yellow or pink may be interpreted as emergency signals in some communities. Know what your boat expects.

Spool Setup: Pre-Attached or Modular?

Should you keep your dSMB and spool separate, or permanently pre-attach them? Each has pros and cons.

Pre-Attached Setup (Preferred for Most Divers):

Faster, cleaner deployment
No fiddling mid-dive
Less chance of dropping or fumbling gear

Separate Setup:

Easier to swap dSMBs or replace line
Higher entanglement risk
Slower to deploy unless practiced

Pro Tip: If pre-attached, use a fixed loop through the dSMB’s bottom ring, not a bolt snap. This eliminates the need to clip or unclip anything while task-loaded.

Inflation Methods Compared

Method	Pros	Cons
Oral	Simple, reliable, no gear required	Requires practice, may need to remove reg
LP Hose	Quick if positioned well	You have to disconnect your drysuit or BCD inflator hose, then reconnect it afterward
CO2 Cartridge	Inflates instantly	Can fail or leak, not airline-friendly

Recommendation: Use oral inflation with a one-way valve. It works everywhere and minimizes complexity.

How to Deploy a dSMB from Depth

Follow this step-by-step process to ensure a clean, controlled deployment:

Look Up — Check for boats, divers, or hazards above.
Unclip and Unspool — If pre-attached, confirm the line is clear and free.
Inflate — Use a few breaths via oral inflation or LP hose. Do not overfill.
Release Gently — Let it rise steadily. Never let go of the spool.
Maintain Line Tension — Keep slight tension to prevent tangles or drift.
Ascend Using It as Reference — Use the line for ascent speed and positioning.

Common Deployment Mistakes

Overinflating — Causes dSMB to fall over or rupture.
Not looking up first — Can hit other divers or a boat hull.
Letting go of the spool — Loses both the dSMB and your visual reference.
Failing to clear the line — Wraps around gear, hoses, or self.
Waiting until too shallow — No time for surface support to see it.

Using a dSMB in Currents or Emergencies

In Currents: Deploy from depth, early in the ascent. Use a larger dSMB. Maintain slight line tension so it stands up in current.
Emergency Surfacing: Deploy while still at depth if separated from the group.
Need for Help: Some divers carry a second dSMB (yellow or pink) as a distress signal, especially on tech dives or liveaboards.
Communicating at the Surface: Use dSMBs with note sleeves to relay written messages if needed.

Maintenance and Inspection

Air Check: Inflate fully on land every few dives to check for leaks.
Valve Inspection: Make sure oral and overpressure valves work smoothly.
Line Check: Look for salt buildup, fraying, or poor winding on the spool.
Storage: Roll and stow it consistently in the same place on every dive. Many divers use their left thigh pocket.

My Setup and Preferences

I carry a 6-foot closed-end Halcyon dSMB with a one-way oral valve. It is permanently attached to a 100-foot spool using a locked-off line loop, not a clip. It lives in my left thigh pocket and comes out on any dive deeper than 20 feet or involving boat pickup. I practice deploying it in low-stress conditions a few times each season.