SMB Deployment: How to Deploy a Surface Marker Buoy Midwater Without Losing Control

Carrying a surface marker buoy (SMB) is standard safety practice, but knowing how to deploy it midwater, in control, and without losing buoyancy is something many divers never formally learn. That becomes a problem when the time comes—because if you rush the deployment or lose your grip, you risk shooting to the surface or dropping your gear.

This guide walks through how to safely and smoothly deploy a delayed surface marker buoy (dSMB)—a signaling device carried uninflated and launched from depth near the end of a dive. The goal: stay neutral, stay flat, and launch cleanly—without creating a mess, a panic, or an ascent.

SMB vs dSMB: What’s the Difference?

This guide focuses on dSMB deployment from midwater—a task every diver should be able to perform before relying on boat pickups or drift dives.

When and Why to Deploy a dSMB

Common situations include:

• Open water ascents without a fixed line
• Surfacing away from the boat
• Currents or drift dives
• Low visibility
• Group separation or delay
• Required by dive ops before surfacing for pickup

If you surface without a marker, boats might not see you—and that becomes a serious safety risk.

Recommended SMB and Spool Setup

Your deployment system should be:

• Closed-end SMB with a one-way valve (like Halcyon’s design)
• Pre-attached Delrin spool (avoid aluminum—they sink fast)
• 100–150 ft of line, depending on your max dive depth
• Double end bolt snap to secure to a D-ring or stow in a pocket
• Spool thread passed through the SMB’s pre-tied loop, not clipped directly

Most SMBs use a push-in oral inflate valve. Halcyon’s design uses a one-way valve, which prevents air from escaping during inflation and doesn’t require manual pressure on the opening.

Note: There is a difference of opinion in the dive community about whether to pre-attach your spool to your SMB. Some divers prefer to clip the two separately and attach them underwater before use. I prefer to store my SMB pre-attached to a Delrin spool in my left pocket—because it simplifies deployment and reduces task loading.

I carry a dSMB on every single dive, regardless of location, depth, or conditions. It’s part of my standard kit—not just for emergencies.

How to Deploy a dSMB Midwater (Step-by-Step)

1. Pause at your stop depth, horizontal and neutral
2. Look up and around—check for boats, divers, or obstacles overhead
3. Retrieve SMB and spool, keeping control of both
4. Unwind 3–5 feet of line to avoid immediate tension
5. Thread the line through the SMB loop (if not pre-rigged)
6. Hold the spool lightly — two fingers
7. Inflate the SMB
8. Let it go — never hold on after inflation
9. Control the spool as line plays out—don’t let it spin freely
10. Stop the spool gently when buoy hits surface
11. Hold or clip the spool during your safety stop and ascent

Inflation Techniques

• Oral inflation (recommended): Controlled, deliberate, and safe
• LP inflator: Fast but can overpower SMB or cause loss of trim—use only if trained
• CO₂ cartridge: Not recommended—single use and hard to control inflation volume

Pre-attaching your spool to the SMB before the dive makes deployment much easier. Trying to clip or tie them together midwater wastes time and increases task load.

Important: You do not need to fully inflate the SMB at depth. One good puff is usually enough to send it up. Top off at the surface if needed.

Why You Should Stay Horizontal

Deploying from trim helps:

• Maintain buoyancy and prevent ascents
• Control the spool with both hands
• Watch the SMB and your buddy
• Prevent kicking the line
• Keep your fins away from silty bottom or reef

Vertical trim increases risk of losing control. Always stay flat during deployment unless conditions require otherwise.

Practice Before You Need It

This isn’t a skill you want to try for the first time in current or at 50 feet.

• Practice deployment in shallow, calm water
• Use a training platform if available
• Integrate SMB launches into your normal safety stop routine
• Try inflating at different depths and with gloves
• Ask a teammate to video you for feedback
• Practice retrieving and stowing your spool cleanly post-deployment