SMB (Surface Marker Buoy) — What It Is and Why It Matters
An SMB (surface marker buoy) is an inflatable, brightly colored tube that a diver deploys from depth to mark their position at the surface for boat captains. Typically orange or yellow and 1 to 1.8 meters tall, an SMB is inflated using a small amount of air from the regulator or an oral inflate valve and sent up on a spool or reel line.
Deploying an SMB is a critical skill for drift diving, decompression stops, and any situation where surfacing away from the boat is expected. A DSMB (delayed surface marker buoy) specifically refers to one deployed from depth during the dive rather than at the surface. Many dive operators consider an SMB mandatory equipment.
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Frequently Asked Questions
When should I deploy an SMB?
Deploy during your safety stop or at the beginning of your ascent from a drift dive, decompression stop, or any dive where you may surface away from the boat. The surface crew watches for your SMB to know where you are and to position the boat for your pickup.
What is the difference between an SMB and a DSMB?
The terms are often used interchangeably. Technically, a DSMB (delayed surface marker buoy) is specifically deployed from depth during the dive, while an SMB can refer to any surface marker. In practice, most divers carry a DSMB and deploy it from their safety stop depth.
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