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 dSMB and Spool Setup

Your deployment system should be:

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

Note: There is a difference of opinion in the dive community about whether to pre-attach your spool to your dSMB. Some divers prefer to clip/store the two separately and attach them underwater before use. I prefer to store my dSMB pre-attached to a Delrin spool in my left pocket because it simplifies deployment and reduces task loading. But I give up instant utility of that spool in other potential situations.

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 pre-rigged SMB Midwater using oral inflation (Step-by-Step)

1. Pause at your stop depth, horizontal and neutral
2. Look up and around checking for boats, divers, or obstacles overhead
3. Retrieve dSMB and spool, keeping control of both
4. Unroll the dSMB fully and "flick" it out and away from you
5. There is now probably several feet of line in the water between the spool and the end of the dSMB
6. Reroll the line up into the spool until the spool is near the oral inflation valve
7. Transfer the "bundle" of spool and oral inflation valve to RIGHT hand so you can control buoyancy (if needed) with left hand like usual
8. Grasp/trap the inflation valve in the fold of skin between your index and thumb
9. Grasp the pool lightly with the index and thumb of your left hand
10. Make one more check of your surroundings and the floating dSMB
11. Remove your regulator with your left hand (which granted is a little awkward / different than when you are usually removing your regulator)
12. Give a 3/4 breath into the dSMB and replace regulator
13. Let it go if you think it has enough air or repeat last step (remember that gas expands as it moves up towards the surface so you do not need or want a fully inflated dSMB at depth)
14. Unclinching your index finger and thumb will release the dSMB, leaving the spool in your right hand and spinning
15. Switch the spool from right hand to left hand - freeing up right hand for air donation in an emergency
16. Control the spool as line plays out
17. Once the dSMB reaches the surface, pull some line down and wind onto the spool to cause tension and the dSMB to "stand up" on the surface
18. Hold the spool during your safety stop and ascent

DO NOT CLIP dSMB/SPOOL TO YOURSELF WHEN INFLATED - IT IS A TANGLE HAZARD AND EXTREMELY DANGEROUS

Inflation Techniques

• Oral inflation (recommended): Controlled, deliberate, and safe
• LP inflator: Fast but requires disconnecting/reconnecting an inflator - temporarily disabling your ability to control buoyancy
• CO₂ cartridge: Single use and simple...but why?

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