What is the function of a surface marker buoy (SMB)?

The function of a surface marker buoy (SMB) is primarily to indicate the diver's position at the surface. When divers are underwater, especially during safety stops or when surfacing, attaching an SMB ensures that their location is visible to boats or other watercraft. This visibility is crucial for ensuring the diver's safety, as it helps prevent potential accidents or collisions with vessels in the area.

In addition to marking the diver's position, the buoy can also act as a signal to retrieve or assist divers, enhancing overall group safety. While other options pertain to important functions within diving, such as gathering samples or signaling distress, they do not relate directly to the primary role of an SMB, which is focused on positioning and visibility at the surface.