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.