How to Choose an SMB

SMB deployment main

What are SMBs?

SMB stands for Safety Marker Buoy. While this may refer to any inflatable surface marker used to mark the location of a group of divers, in this article we will be talking mainly about Delayed Surface Marker Buoys. DSMBs are also known as safety sausages. The main difference between the two is that the DSMBs are an inflatable tube, which are inflated at depth and released to the surface, rather than inflated on the surface. Hence the term “delayed”.

In this case, SMBs are used for a variety of reasons. They primarily serve as a marker to the dive boat to indicate your location. They may also provide a visual reference during ascents, and especially during your safety stops. For instance, if you’re doing a safety stop in a current, you may drift away from the boat; and so the SMB would be a clear marker of your location to the dive boat.

Some operators and liveaboards consider SMBs a mandatory piece of dive safety equipment. Even if you’re diving with an operator who doesnt count SMBs as compulsory, it is still a very useful equipment to have, in the unlikely events you get separated from the dive group or drift away from the boat.

There are lots of different types of SMBs, varying in sizes, inflation methods, colours and deployment . Let’s examine the variations below.

Closed circuit vs open-end SMBsopen end SMB

Open end SMBs are exactly what they sound like: the bottom is open and does not seal. This means that they’re usually quite easy to inflate. When back on the surface, they’re also very easy to deflate for storage. On the downside, air does tend to escape from the unsealed bottom. To combat this, most open end SMBs have a weight at the bottom to reduce escaping air as it breaches the surface, but still require tension on the line to maintain inflated.

Closed circuit SMBs on the other hand, are sealed tubes, that come equipped with valves. Because they’re sealed, closed circuit SMBs are generally much easier to keep inflated.

Both types of SMBs have their pros and cons. Part of that is the inflation method, which is discussed in detail in the next section.

closed circuit SMBGenerally speaking, open-end SMBs are easier to deploy at depth than closed circuit SMBs. However, open-end SMBs may not be as easy to keep inflated and visible at depth.

Inflation method

SMBs can be inflated in a variety of ways, depending on whether they’re closed circuit or open. Open-end SMBs can be inflated with by purging your alternate air source directly into it. Another method preferred by the pros is to hold open the end of the SMB and catch their exhaust (exhalation) bubbles directly into the SMB.

closed circuit SMB oral inflator valveAs for closed circuit SMBs, they’re usually inflated orally. In this method, you would then inhale, remove your regulator out of your mouth, seal your lips around the valve of the SMB, open the valve, exhale and then replace your mouthpiece. Some of the larger closed circuit SMBs come equipped with a valve that enables you to use your low pressure inflator hose to inflate the SMB.

Size matters

The size of your SMB depends on where you’re diving. When diving in areas with relatively calm seas, little or no current, and low wave heights, a small SMB is good enough. These are up to a metre long and relatively thin in diameter. However, if you’re diving somewhere with tall, white capped waves, or if you’re doing a drift dive where you’re likely to drift quite far, a larger SMB would be wise. These are up to 2m or more, and are relatively thick in diameter. Personally, I carry two SMBs with me on dive trips – a small one and a large one. Just before the dive, I select one to bring with me on the dive, choosing it based on the local sea conditions.

SMB colour yellow or orangeColours

Most SMBs come in either bright orange or yellow. So long as it’s a bright, outstanding colour that is easily spotted, colour shouldn’t be much of a factor in choosing your SMB. In addition to colour, some SMBs come with a reflective strip which increases visibility during the day, ie. it can be spotted at much greater distances, and is useful for night dives as well.

Reels, spools, line and weight systems

Since we’re talking about DSMBs, we need a way to launch the SMB from depth. This is where a line would come in. If you’re planning to launch your SMB for your 5m safety stop, a 20ft finger spool would do the trick. However, if you’d like to launch it from greater depths, you may want to consider a hand reel. Do note however, that hand reels are more prone to failure. Alternatively, some divers prefer using a line attached to a weight. When deploying, they would then drop the weight first, then proceed to inflate the SMB and launch it.

Suggested SMBsAropec SMB


Aropec Safety Pack – SGD25 

  • PVC open-end 1.7m long SMB with weights at the bottom to prevent air from escaping
  • affordable
  • comes with bright pouch with a ring for attachment and whistle

Aropec Closed Circuit SMB – SGD30

  • closed circuit 1m long SMB with oral inflator and dump valve

seac sub smbSEAC Sub SMB – SGD35


  • PVC open-end 1.3m long SMB with weights at the bottom to prevent air from escaping
  • packaged in a velcro pouch that has a side hook on each end for easy attachment to equipment
  • the pouch remains attached to SMB during deployment – no more hassles of lost pouches!
  • comes with a line

Mares Cruise Safe Bag – SGD45mares cruise safety bag

  • features an open-end 1.2m long SMB with weights at the bottom to prevent air from escaping and a D-ring for easy attachment to line
  • equipped with 10m of line with a clip at the end for easy attachment to SMB and a 150g lead weight tied at the other end
  • comes with signalling mirror with lanyard
  • all packaged in a velcro pouch that has a side hook as well a a rear fastening system which is convenient to attach to a belt or equipment

aropec finger reel spoolFinger spool – SGD20 – SGD35

  • Comes with double-end brass clip
  • Variations of length: 20m, 30m, 45m
  • Variations of colour: white, yellow, orange
  • Variations with and without handle


So now you have your SMB, but how do you deploy it? Watch the video below!