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?

Type When It’s Deployed Use Case
SMB On surface or before dive Station marker, shore dive flag
dSMB During the dive, usually at stop depth Midwater signal to surface, ascent marker

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)

There are several different methods - I prefer the one demonstrated by Achim with InnerSpace Explorers

  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. With the LEFT hand, grasp the spool and dSMB
  6. With the RIGHT hand, unclip the double-ender from the spool and clip the double ender to the right chest DRing
  7. Reroll the line up into the spool until the spool is near the oral inflation valve and no extra line is in the water
  8. With the RIGHT hand, grasp the oral inflation valve in the webing of your RIGHT hand
  9. With the RIGHT hand, grasp the spool lightly between the index finger and thumb of the RIGHT hand
  10. ...this leaves the LEFT hand available for controlling buoyancy during inflation as necessary...
  11. With the LEFT hand, remove your regulator (which is a little awkward compared to normal removal)
  12. Give a 3/4 breath into the dSMB and replace regulator
  13. ...Repeat last step until inflated enough...
  14. Transfer spool to LEFT hand and seperate the spool from the dSBM aproximately shoulder length apart
  15. Release the dSMB from the RIGHT hand - freeing up right hand for air donation in an emergency
  16. The dSMB will shoot to the surface while the spool spins between the index finger and thumb of your LEFT hand
  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. Remove double-ender from right chest DRing and clip the line to the spool so it cannot unravel and descend
  19. Hold the spool during your safety stop
  20. As you ascend after the safety stop, slowly roll the line onto the spool so as to not be a tangle hazard
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
  • Regulator inflation: Requires an open ended dSMB and I don't prefer them because they are not as stable at the surface
  • LP inflator: Fast but requires disconnecting/reconnecting an inflator - temporarily disabling your ability to control buoyancy
  • CO2 cartridge: Single use and simple, but limited practicality

Practice Before You Need It

This is not 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