SMB deployment

The Secret Sauce for Surface Marker Buoy (SMB) Deployment

by Jon Kieren:

There is more than one way to skin a cat, so to speak. While often the subject of a very heated, quite humorous debate, technical diving is not exempt from this saying. One of the more common skills often debated is Surface Marker Buoy (SMB) deployment. There are many variations to performing this skill as well as selecting the equipment to use, but the overall objective remains the same: deploy an SMB on an ascent line without shooting yourself to the surface.

Because there are so many variations of SMBs, lift bags, reels, finger spools, etc., this article will focus on one specific aspect of deploying an SMB: methods for inflating the SMB.

  • Regulator Second Stage: This is a common practice and makes it easy to add enough gas to the SMB in order for it to stand tall in the water and be easily noticed. However, it does have several drawbacks; for example, it’s never a good idea to intentionally free flow a regulator on a technical dive, especially in cold water, as it could result in a significant loss of gas.
  • Primary Regulator Exhaust: This method is very quick and efficient, it does not require any special equipment and it is very popular. However, it should be noted it is far from perfect. It is difficult to tell if the exhaled gas is making it into the SMB, it is difficult to get sufficient gas into the SMB at a shallow depth without causing a significant buoyancy shift, and it requires the diver to hold the SMB close to their body when adding gas (increasing risk of entanglement).
  • BCD Power Inflator: Extremely effective for rebreather divers who do not have an exhaust to inflate the SMB, this method is quick, does not require any special equipment, and makes it easy to add plenty of gas without creating a buoyancy shift. The diver simply places the exhaust of their BCD inflator into the bottom of the SMB and depresses both the inflate and deflate buttons simultaneously, releasing gas straight into the SMB. This method does have a couple of small drawbacks. Mainly that the SMB needs to be close to the diver’s body in order for the power inflator to reach and that if the diver does not depress the deflate button entirely, the gas may inflate the diver’s BCD, causing them to become positively buoyant.
  • Oral inflation: One of the simplest methods of SMB deployment is using the oral inflation valve. The diver holds both the SMB and spool in one hand and removes their primary regulator from their mouth with the other hand and blows into the oral inflation valve. This works well when using a smaller SMB and a finger spool, but if you are deploying from depth you may need more line than is available on your finger spool. You will then need to use a primary reel, which is very difficult to manage along with the SMB, with one hand. It is also not appropriate for rebreather divers.
  • Air Nozzle Low Pressure Inflator Attachment: Very popular with both open circuit and rebreather divers, the air nozzle attaches to a low pressure inflator hose and is typically rigged on a deco or stage bottle. The nozzle is used to blow gas into the SMB; it is very convenient and allows the SMB and reel to be held out away from the diver’s body. The main downside is it requires a special piece of equipment that adds an additional failure point.

TDI SMB deploy

Just recently I was on a tech boat and saw a fellow diver struggling to kit up on the boat, apparently the air nozzle on his deco bottle was free flowing. He was worried that if he needed to remove it, he would not know how to deploy his SMB without it. On a wreck in strong current at 60m/200ft is not the time to be attempting new SMB deployment methods.

The list continues on from here; however, I’m sure you can see that there are many variations to this critical skill. All of these variations have their own strengths and weaknesses, and a diver should choose a method that suits them best. No matter what method you decide on, it’s extremely important to receive proper training with a qualified instructor and practice until it is second nature.

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20 replies
  1. Raoul Claessen
    Raoul Claessen says:


    Personally I am using SMB’s from AP diving England. They come with a small air bottle for infaltion. The airbottle can also be replaced by a connector to connect with the LP inflator hose.
    Using the airbottle to inflate has the advantage of not have to use a second stage to fill the SMB and preventing freeflow situations or antanglement durig a dive.

    Kind regards,
    Raoul Claessen
    TDI SDI Instructor #9576

  2. gilles gaubert
    gilles gaubert says:

    Cool article !
    You forgot to mention the easiest of them all : buy one of these cool SMB with small tank attached (such as the ones made by APD)
    This is a cool one for rebreather divers who dont want to go for their bail out gases (even if this is a very small volume…)

  3. stepen phillips
    stepen phillips says:

    One other method that is very popular with rebreather divers is were the small inflation bottle is attched to the SMB, making it self contained and easy deployment as long as the inflation bottle is charged before the dive !!!!

  4. Alex Tasker
    Alex Tasker says:

    There’s no substitute for practice, but a crack bottle or CO2 cartridge does make for a quick and easy deployment, even from shallow depths. You know you’re going to get a full bag, and there is a small delay between triggering the inflation and a big upward pull on your reel or spool.

  5. Jon Parlour
    Jon Parlour says:

    I have a mini air cylinder attached to my DSMB, which saves using primary or secondary gas supplies and enables me to ensure good separation (I hold it out at arms length when deploying). Downside is you have to top up cylinder between dives. So I have a second mini cylinder in bag for second dive of day. A dive buddy of mine has disposable CO2 cartridges in his DSMB, he buys in bulk and says they are inexpensive. Both these methods minimise entanglement risk. We both dive CCRs and find it saves using gas from life support system.

  6. Robert
    Robert says:

    While this article presents a very brief discussion of various SMB inflation methods, it presents nothing in the way of advancing the methodologies discussed or improved techniques. So what is the “secret sauce” mentioned in the title?
    The article is just a series of statements with no purpose or goal. What was the intent here, practice?

  7. John L.
    John L. says:

    Inflating the SMB includes several methods that all work. The “secret sauce” involves how to properly hold your spool while the SMB flies to the surface, and how to properly wrap and stow your SMB.

  8. Jim Collins
    Jim Collins says:

    The small tank SMBs are great but they are only good for a year until they should get Visual Inspection and five years for Hydro. Since you open the valve on the bottom and they go to the top were the pressure goes to zero the tank tends to get water in it. I just opened an old one and looked inside and it was kind of scary with salt crystals. There is also the issue with flying with these.

  9. Richard Taylor
    Richard Taylor says:

    A good, well balanced article! Missing the cat ridge DSMB popularised in the UK, but aside from that a good cover of different techniques! Thanks!!

  10. Steve B
    Steve B says:

    Where’s the beef… I mean sauce? I’d like to an article/video on how to use co2 cartridges mentioned in these replys.

  11. Ben Reymenants
    Ben Reymenants says:

    Good article!
    I’m with Jim. I’ve had the small bottle SMB and it’s not only bulky, it’s also a liability. It corrodes fast, salt gets in and divers forget to service. One part missing is the inflator hose attachment point; a very popular item with CCR divers; a plastic or steel inflator nozzle without barb is permanently attached to the SMB and any LP inflator hose can be used. Dexterity and training is key here, but once mastered, it’s a very handy and clean inflation method

  12. Michael Matzinger
    Michael Matzinger says:

    Good list. I use SMBs that have a connector to use standard inflator hose (can also inflate orally or with a second stage). It is great for tech/rebreather dives all it needs is a standard LPI hose on the deco/bailout bottle or use the hose going to your BC. This method makes for a fast, easy deployment and with practice can be done with one hand.

  13. Dean Coleman
    Dean Coleman says:

    I just tie my reel off to my buddy and inflate his/ her BCD, this normally provides sufficient flotation to hold stops.

  14. Matthew Mudge
    Matthew Mudge says:

    IMHO, all the above methods make launching a DSMB a two man job.
    By far and away the best DSMB for both ease of use and safety is the type made by Buddy with a refillable crack bottle attached.
    If the bottle fails or you forget to fill it you can still resort to any of the methods described in the article above.
    Using the crack bottle method has one significant advantage over a CO2 cartridge, i.e., before launching the DSMB to the surface it is possible to open the crack bottle for a moment then re-seal it, letting a small amount of air into the DSMB thus letting the DSMB take shape and align itself upwards. The diver then has plenty of time to sort themselves out, ensure they will not become entangled with the line/reel and be dragged to the surface, signal to their buddy when they’re ready to launch the DSMB, check above them before launching the DSMB and so on.
    If you find yourself in an emergency/low air situation using the crack bottle does not reduce your own remaining and limited supply of air.
    Using a crack bottle makes launching a DSMB a reasonably quick one man task rather than a slow two man task which might be particularly important/relevant in a lost/separated from buddy scenario.
    The buddy DSMBs are available in the usual Orange or the generally accepted bright lime/yellow “I’m in trouble” colour, the use of which will invariably be in an emergency/low air situation.

    Reference visual inspection and Hydro tests, such crack bottles are not used for “Breathing Air” and carry no such stickers so I believe this is a moot point. The main thing to remember is that they may well get some water in them so make sure when refilling them from a full tank of back gas that the bottle is placed in such a way (i.e., valve upwards and base downwards) that any water that might be present cannot get from the crack bottle into your main cylinder.
    Any water that might get into the crack bottle can be cleared by refilling it, holding it upside down and emptying it (whilst not attached to the DSMB !!), several times as necessary.

    Flying with crack bottles has never presented me with a problem. I pack the bottles in my suitcase with my BCD etc, having first made sure the bottle is empty and the valve left in the Open position.

    Finally, I believe the real “Sauce” for deploying a DSMB is practice, practice and more practice.

    Kind regards and safe diving.

  15. John Orr
    John Orr says:

    I also go for the Buddy AP Valves crack bottle in UK, a bit heavy for overseas travel with some airlines stingy baggage allowance. You don’t have to worry about how you hold it to charge it as there is no way water can get into your main cylinder if it has a full charge. That’s another thing, make sure that your charging cylinder is at least 200Bar. Overseas I remove my drysuit hose from my 1st stage and replace it with a longer hose and a black flexible air gun filling nozzle at the end. Now having the same number of fail points as my UK configuration. One thing not mentioned here is the reel. I only use a reel that can be locked in the free running position. Kent Tooling for UK (robust but heavy) and the small Buddy travel reel for overseas. Both can be locked in the free running position which I think is an important safety feature. The key to safety is practice practice practice. Don’t take the easy way out and always let your buddy do it. Also if possible have your set up ready to go, i.e. inflation bag attached to the line. One of the main dangers of this is when you may need to deploy it quickly and this may be in mid water. DSMB deployment should be done slowly and controlled, if you rush you are more liable to make a mistake. Remember, these things can lead to serious injury or worse if you get tangled, treat with respect . Also due to current make sure you have enough line. For example if you are at 30m you will need 45m of line (add 1/2 to your required depth at deployment), this will allow for up to a 45 degree angle.

  16. Pat Wolfe
    Pat Wolfe says:

    Here in the Great Lakes most of us use the primary exhaust method. Using the second stage increases the risk of a free flow, inflationary gadgets add failure points, disconnecting a bc inflator adds task loading especially with dry gloves on. Having a dedicated inflator hose or blow gun works but adds more failure points. I prefer to keep my techniques simple, low tech, and I practice.

  17. Soren Knudsen
    Soren Knudsen says:

    Either of the above methods will work, provided you have ample time to practise. (alternate airsource excepted for colder climates) I think it’s a good thing, that entry level diving courses are now starting to have DSMB deployment as an integrated part – it should have been that from the beginning. I have seen fully certified divemasters, who still struggle with it.

    The use of a pressurerized mini bottle is neat… but a but of a gimmick to me. Would you cancel a dive if it didn’t work? If not, then you’d still have to learn to launch the DSMB in an alternate fashion.

  18. Trevor Brown
    Trevor Brown says:

    I worry about Crack bottles as they completely empty, themselves at surface. This state could allow in small drops of water, which could lead to rust. Remember we are self filling a cylinder to 200 bar+


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