What distinguishes a surface marker buoy (SMB) from a delayed surface marker buoy (DSMB)?

The distinction between a surface marker buoy (SMB) and a delayed surface marker buoy (DSMB) primarily lies in the timing and context of their inflation and deployment. A surface marker buoy is typically inflated and deployed at the surface before a dive begins, while a delayed surface marker buoy is designed to be inflated underwater, usually at depth, and then ascended to the surface.

The function of a DSMB is often to signal one’s presence at the surface while still underwater, which is particularly useful for notifying a surface support team of the diver's location following a safety stop or during exploratory dives. This reflects the purpose and operational context of each type of buoy: the SMB generally marks a surface position, whereas the DSMB is used to indicate where a diver is ascending from or moving towards, facilitating safety and awareness during the ascent phase of a dive.

Understanding this difference is crucial for dive safety, particularly in areas with boat traffic or when diving with multiple divers, as it enhances communication and visibility to support teams or other divers.