## What is SMT in Scuba Diving?

SMT, or Surface Marker Buoy (SMB), is a device used in scuba diving to indicate the diver’s location to boat traffic, other divers, or rescue personnel. It is typically a long, thin, inflatable tube that is attached to a line. The line is then attached to the diver’s harness or buoyancy compensator (BCD).

Purpose of an SMB

The primary purpose of an SMB is to increase the visibility of the diver in the water. This is especially important in low-visibility conditions, such as when diving in murky water or at night. By deploying an SMB, the diver can alert surface support of their location and assist in guiding them back to the boat.

Types of SMBs

There are two main types of SMBs:

Manual SMBs: These SMBs require the diver to manually inflate them using their own breath. They are typically smaller and more portable than automatic SMBs.
Automatic SMBs: These SMBs are inflated automatically when the diver pulls on a release cord. They are typically larger and more expensive than manual SMBs.

When to Use an SMB

SMBs should be deployed in the following situations:

When diving in low-visibility conditions
When diving in areas with heavy boat traffic
When diving at night
When lost or separated from the dive boat

How to Use an SMB

To use an SMB, the diver should:

1. Inflate the SMB using their breath or by pulling on the release cord.
2. Attach the line to their harness or BCD.
3. Hold the SMB vertically in the water.
4. Wave the SMB to attract attention.

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Benefits of Using an SMB

Using an SMB provides the following benefits:

Increased visibility: SMBs make the diver more visible to boat traffic, other divers, and rescue personnel.
Increased safety: SMBs help to ensure that the diver can be easily located and assisted in the event of an emergency.
Improved communication: SMBs can be used to send signals to surface support, such as a “come and get me” signal or a “I’m okay” signal.


SMBs are an essential piece of safety equipment for scuba divers. They increase the diver’s visibility in the water and provide a way to signal for assistance in the event of an emergency. All scuba divers should be familiar with the use of SMBs and should carry one on every dive.

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