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The Importance of Delayed Surface Marker Buoys (DSMBs) in Scuba Diving

Delayed surface marker buoys, or DSMBs, hold immense significance among scuba divers as a crucial safety tool. Regrettably, they tend to be underutilized, and numerous inexperienced divers lack the necessary knowledge to deploy them effectively. The array of names used for dive floats can be perplexing, leaving many divers puzzled. If you find yourself curious about the purpose of these devices and uncertain about their proper usage, fret not, as we are here to assist you!

What is an SMB?

Scuba diving is a thrilling and adventurous activity that allows us to explore the beauty of the underwater world. However, it is not without its risks. Divers face various challenges, one of which is surfacing safely after a dive. Here's where Delayed Surface Marker Buoys (SMBs) come into play. An SMB is an inflatable buoy used by divers to signal their presence to not just boats or other watercraft but anyone on the surface.

SMB vs. DSMB: Decoding the Difference

As diving novices may find the terminologies bewildering, let's start by clarifying the acronyms. SMB stands for "Surface Marker Buoy," whereas DSMB represents "Delayed Surface Marker Buoy."

Surface Marker Buoys serve as vibrant inflatable tubes that divers use to indicate their location from the surface. Some are designed from thin rubber for emergency situations, fitting conveniently into a BCD (Buoyancy Control Device) pocket. Rental BCDs often include these buoys, making it crucial for all divers to master their usage at the surface.

In certain regions, diving marker flags or dive floats also fall under the surface marker buoy category. In shallow coastal areas with significant boat traffic, it is customary to tow a dive marker float with a diver down flag at the surface throughout the dive.

On the other hand, Delayed Surface Marker Buoys (DSMBs) offer versatility. The "delayed" aspect signifies that divers can deploy them during the dive, typically before performing the safety stop, instead of inflating them at the dive's outset and towing them throughout the dive.

To send the DSMB to the surface while remaining connected to it, divers partially fill the buoy with air at depth and hold onto a reel. Compared to their surface-only counterparts, these DSMBs come with slightly more advanced features.

The Importance of Using SMBs

Enhanced Safety

Safety should always be the top priority for any diver. SMBs act as a visual marker that lets boat operators know the diver's position, reducing the risk of accidents or collisions on the surface. By deploying an SMB during ascent, divers can maintain a safe distance from the boat, preventing potential entanglement hazards.

Easy Location Identification

Spotting divers who are surfacing from below can be challenging in open water. SMBs, with their bright colours and easy visibility from a distance, facilitate the surface support team in locating divers. This simple yet effective signalling device significantly enhances the overall safety of the diving operation.

Prevents Separation

Diving groups may accidentally get separated during a dive, especially in strong currents or low visibility conditions. SMBs provide a clear reference point on the surface, helping divers reunite after the dive. It is a vital tool in avoiding potential search and rescue situations.

Communication Tool

Besides serving as a safety marker, SMBs can also be used as a communication tool. Divers can attach reels or lines to their SMBs, allowing them to send messages or signals to the surface support team. This two-way communication system further enhances diver safety.

Different Types of SMBs

There are several types of SMBs available, each with its unique features and purposes. Let's take a look at some of the most common ones:

Open-Ended SMB

The open-ended SMB is the most basic and widely used type. It is a simple tube-like inflatable buoy with an open bottom. Divers can orally inflate it on the surface, and it can be easily deflated and compacted for storage. The open-ended design allows the SMB to vent excess air automatically as the diver ascends.

Closed-Ended SMB

The closed-ended SMB, as the name suggests, has a sealed bottom. It is inflated using a low-pressure inflator hose from the diver's regulator. Unlike the open-ended SMB, this type retains all the air that goes into it, providing a continuous buoyancy reference on the surface.

Self-Sealing SMB

The self-sealing SMB combines the features of both open-ended and closed-ended SMBs. It automatically traps the air inside when inflated orally, similar to a closed-ended SMB. However, it can also be inflated using a regulator hose, like an open-ended SMB.

Safety concerns with DSMB deployment

One major safety risk associated with deploying a DSMB is the potential for entanglement. When the DSMB is released, there is a chance that the diver could be unexpectedly pulled upward, leading to an uncontrolled ascent and the risk of decompression sickness. Before releasing the DSMB, it is crucial to always check above you to ensure that no other divers are shallower and at risk of getting entangled.

Another safety consideration is the possibility of the reel jamming or snagging after the DSMB has been deployed. If this situation occurs, it is important to promptly release the reel and ascend safely to the surface.

It is essential never to connect the DSMB reel or spool to your BCD once it has been deployed. Doing so could result in serious consequences if the DSMB becomes snagged by a passing boat or is pulled by strong currents, potentially causing a rapid and uncontrollable ascent to the surface.

The Neglected Importance of SMBs

Despite their crucial role in scuba diving safety, SMBs are often overlooked or underestimated by some divers. Factors such as budget constraints, lack of awareness, or a false sense of security may lead some divers to forego carrying an SMB during their dives.

However, every diver should consider SMBs as an essential part of their diving equipment. Divers must remember that it's better to have an SMB and not need it than to need one and not have it. SMBs can make a significant difference in emergency situations, where every second counts.

Practising the Deployment of SMBs

Practising the deployment of Delayed Surface Marker Buoys (SMBs) on every dive is crucial for the safety and well-being of divers. It is a skill that requires practice and proper training to avoid potential hazards and accidents. By dedicating time to improve SMB deployment techniques, divers can enhance team coordination, communication, and overall safety during their diving adventures.


In conclusion, Delayed Surface Marker Buoys (SMBs) are not just inflatable buoys; they are crucial safety tools that every diver should include in their gear. From enhancing diver safety to acting as communication tools, SMBs play a vital role in ensuring a smooth and secure diving experience.



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