Surface Marker Yeaahh Buoys!

This month let’s talk about surface marker buoys (SMBs), a mysterious device which isn’t officially taught as part of any course but is an essential piece of kit in many parts of the world.

SMBs are essential for a number of reasons, most importantly they mark the location of the diver in the water. This means skippers can follow divers in a current and also see where they’re surfacing. Other boat traffic also can see the buoy and avoid driving over you. The other big advantage is that when they’re deployed underwater the line creates a visual reference for the diver to use when making a long ascent from depth.

They also provide an endless source of comic amusement at the end of the dive as divers vie to see who has the stiffest sausage etc etc.

First off some basic facts: When divers talk about delayed SMBs they basically mean one that is sent up from depth instead of inflated on the surface and that is the most commonly used type. Second some terminology: SMBs have lots of slang terms that mainly say more about the diver:

  • Safety sausage: Most commonly used as a term by people who dive in shallow bays in South East Asia or just don’t know what they’re talking about.
  • Bag: A very teccie term that will make you look well hard and knowledgeable, as in ‘When I reach 20m I’ll throw a bag’.
  • Blob: A deeply unpleasant term mainly used by gruffly spoken men wearing drysuits that are 50% gaffer tape.
  • Big Red Diving Ding Dong: I made this one up.

Due to the fact that walking into a dive shop and asking for a sausage, a bag or a blob are likely to have mixed results I highly recommend using the term SMB.

So given that you can spend anything between about £15-180 what should you be looking for in your SMB?

Let’s deal with colour first. Unless you’re off on a great big technical dive then red is the only acceptable colour. Yellow means there’s an emergency under the water and those SMBs that are yellow on one side and red on the other are the worst thing ever made by a human being giving the confusing message that you are alternating between life and death to the skipper as the buoy revolves on the surface of the water.

Next up is the design: If you don’t spend much money then you can get one of those sock style ones which is just an empty tube open at one end. If you’re really lucky there might be some lead stuck on the bottom of the tube to help it stand up in the water. These ones are really shit. The main problem is that you put some air in them under the water and then send them up to the surface where they fall to one side and dump half the air out thereby massively reducing their lift and visibility on the surface which isn’t very useful given that’s the main point of them.

The main feature to look for on any SMB is that it will seal. There are different ways of achieving this, the cheaper ones have an opening at the bottom through which you can add air and then a simple design that means the air can’t get back through. These ones are called ‘self sealing’ and the main advantage is that once the airs in, it stays in so these buoys stay fully inflated and visible on the surface. To get the air out you just use a dump valve.

Dump valve on SMB

A dump valve on the side of a self sealing SMB

SMBs also come in various sizes, the most common is around 1.4m tall and these ones are definitely preferable in UK waters where the visibility and size really counts. You can also get smaller 1m ‘single breath’ SMBs which are great for the tropics or as back ups.

Frog SMBs

2 different sized Frog SMBs. These are much cheaper than the Halcyon ones and you don’t have a blue swastika on them either.

So how do you inflate your SMB? There are a few popular methods, so let’s look at the pros and cons now:

Using your octo: This is one of the oldest methods of inflating your SMB and many people prefer this. There are 2 main issues with this method. Firstly deliberately purging a reg in colder water (like the good old UK) can precipitate a free flow and secondly as far as I can work out this method requires 3 arms which unless you are the T1000 is unlikely. Therefore this would be the most inadvisable method.


The T1000 flies his helicopter to the dive site shortly before using his 3 arms to inflate his SMB with his octopus which results in a massive free flow so that he ends up doing a fast ascent (he was also irresponsibly solo diving) and he gets a nasty bend which ends up costing loads of money in hospital bills because Skynet had only taken out basic travel insurance with Insurengo instead of a dedicated diving insurer like DAN.


Using exhaled breath: Depending on the style of your SMB this might be your only other option but it is a good one. The great thing about this method is that, especially with smaller SMBs, you can deploy them without even affecting your buoyancy too much. If you’re neutrally buoyant with a full breath of air in the lungs when you exhale into the SMB, hey presto you’re still neutral! The only real disadvantage of this method is the possibility of getting your reg tangled in the line of your reel.

Using an inflator: Some SMBs including the excellent Frog SMBs have an inflator on them which allows you to either orally inflate them or use a standard BCD or drysuit inflator hose. The connector cannot ‘stick’ to the inflator valve so once the air is in it just pops off the end. These ones are really great because you have a variety of options to inflate them.

Inflator on SMB

An inflator which can be used orally or with an LP hose


Crack bottles: At the simplest end of the scale we have crack bottle deployment. These SMBs use a tiny cylinder which you charge from your main tank to fill the SMB. When you’re ready to deploy you just open the cylinder and the SMB fills up. Simples. The disadvantages of this method are the cost (quite a bit more) and also the fact that the cylinder gets water in it when it empties that can then end up in the other tank when you refill it. This can drastically shorten the life of your dive tanks

If you’re a newbie to SMB usage then the SMB distinctive course can be a handy way of getting a chance to use different SMBs and reels (more of which next month) and try out different deployment techniques with an instructor. We can run these anytime we’re at open water . Check out more details here:

For any other advice on SMBs and reels just pop into the shop anytime!


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