Surface Marker Buoys (SMB) are often the ugly duckling for scuba divers. Particularly divers who do not have their own BCDs are often reluctant to add this bulky item to their kit. More experienced divers will get this relatively cheap item, clip it on their BCD and then never use it again - forgetting how to use it altogether.
We at Insider Divers always make it a mandatory packing item for every trip. The discussion is often "Do I really need this?" or "I have this really small SMB, is that sufficient?" and so on.
The short answer - yes you need it! And it needs to be the right type!
On location we insist that everyone practices SMB deployment at the end of our check dive. Big surprise - even experienced divers often have trouble deploying a SMB. It requires practice as there are a surprising number of steps to go through. Read about those at the bottom of the blog post.
"Why do I need an SMB?"
This is often the No. 1 question - here are the reasons why.
1) To mark the area where you ascend
Before ascending someone marks the group position. This is to make sure boats around you know that there are divers below. Even non-dive boats will understand this signal. If you ascend without a SMB you put yourself at risk of injury.
2) Provide visual reference from afar
If there is no boat around to pick you up, the SMB will help to gain their attention. Boats can spot a 1.5m balloon sticking out of the water much easier than just a wet head. If further away, you can also wave with a SMB (only closed type - see below).
3) Location & depth for your safety stop
We often want to avoid ascending on the reef and therefore swim away before ascending. In current dives it is common to do the safety stop in the blue.
With nothing but blue ocean below divers often find it hard to keep their safety stop depth steady. Here a SMB is a great marker for the depth. If drifting while doing the safety stop, the boat can follow your movement. (Some people call it a DSMB for Decompression SMB - so it is meant to help you hold your depth during safety stop)
When ascending the line of the SMB provides a visual reference. When you roll it up yourself it is also handy for practicing a slow ascend along the line.
4) Provide a floatation for tired divers at the surface
A SMB can serve as an additional float if you are tired and having to wait at the surface for your pick-up. If you have a panicking diver (for example because the boat is not in sight) it will provide a a great sense of security if the diver can hold onto the SMB.
"But the divemaster has a SMB!"
You could of course consider outsourcing this to your dive master but .....
5) You want to be able to take care of yourself.
The more experienced you are the more likely you and your buddy might venture away from the group and do your own thing - and you should, its great fun. But now as a smaller group it is even more important to ascend with a SMB - so you need your own.
Avoid potential emergencies
There is a reason why it is mandatory to use. There are common situations where you will need it and where not having it could turn a normal situation into an emergency.
6) No more divemaster
Losing your divemaster is no emergency. It can become one if you do not know where to ascend and you have no SMB. When you get separated from the group, you want to be able to mark the surface. You don't want to find yourself in a situation where no-one around you has a SMB.
7) Cannot find the reef
If you are diving on a reef and maybe the current pushes you out. Now you need to make sure that you tell the boat where you are. Again, no need to panic as long as you or someone around you has a SMB.
"My partner always carries one and we always dive together. So I do not need one."
8) Lost buddy
Of course you plan to stay with your buddy. But sometimes things happen and suddenly you are separated. When you get separated from your buddy (and your group) you need to ascend by yourself making it even more important to have an SMB. This is ultimately why you have to have YOUR OWN SMB.
"Divemaster has it anyway" - classic argument but please see 5) , 6) and 8) - trust that it will happen one day.
"My buddy has it" - yes, but as mentioned in 8) you might lose your buddy.
"I can just blow bubbles to mark the surface" - have you ever tried spotting divers in choppy waters - experienced boat captains can... sometimes. Often its impossible. And non-dive boats will certainly not notice you.
"I do not want to buy an extra device." - Its a very small addition to your gear but adds so much safety. Why take the risk?
"Can I rent a SMB?" - Sure you can but then the device you use will always be different. It is much better to get proficient at using your own device. Also, rental SMBs are often in a poor state and very rarely do they provide a reel.
There are various types of SMBs but there is only one set up that I recommend. Below I have listed the recommended, as well as non-recommended types and why I do not think they are useful.
Open bottom, one direction air flow, with a reel
- with valve and oral tube
- opening at bottom which only allows one way flow of air
- 20m is enough
Double header bolt snap
This is the safest SMB and it is the most convenient way to deploy. See below how to deploy.
Avoid these SMBs for the following reasons:
- the line has to be unrolled which takes time
- huge entanglement issues
- when unrolled it is easy to wrap around coral and cause damage
Open bottom without one-way air flow mechanism
- at the surface the SMB collapses as the air can escape
- cannot be waved at the surface
- cannot be used as a float at the surface
Oral inflation only
- usually very small
- does not mark the surface well
- cannot be used as a float at the surface
- you have to take your regulator out to inflate. This might be fine in a comfortable position, but if you are under stress due it will increase your anxiousness
No line or reel
- you can only deploy at the surface or just below - risk of getting run over by a boat
- cannot be used as a line for your safety stop
In summary, there is only one type of SMB that I can recommend. These are easy to get online and they cost a fraction of all other dive items, let alone the cost of a dive trip. Please do not save on this essential item!
How to deploy
On all our trips we coach our divers on this before the check out dive. It can take a while to get proficient, but do not take this a reason not to practice - it is your emergency device so you should know how to use it.
Everyone does it differently but here is a basic run-down of my preferred way
1) Make sure you are neutrally buoyant and at roughly 5-6m or slightly deeper
2) Unclip SMB from BCD
3) Add a tiny bit of air into the SMB to make the top float
- My personal preference is oral inflation. Bring the opening of the SMB to the exhaust of your regulator, tilt to the side and exhale (Image on left)
The bubbles will enter and fill the SMB (only works for open bottom SMBs)
- you can also use your alternate regulator to directly inflate the SMB but you risk entanglement
- or you can orally inflate through the tube (as pictured above) but you need to take your regulator out of your mouth
4) Unclip SMB from reel (and store clip on BCD)
5) Put middle finger through reel and connect with thumb
6) Line should be on the outside of the reel (to avoid entangling thumb)
7) Exhale twice into opening and let go of SMB
8) Let reel run over middle finger until SMB at surface and then pull
Watch your depth! (by keeping an eye on your computer)
Sounds like a lot to think of - thats correct. It might take 2-3 times to get it right but you will see how much safer and more independent you feel after that!
Thats it. Hope you enjoyed reading this long blog post about such a small scuba equipment item.
(The diver in this article is Sarah Richard from GirlsThatScuba. If you want to buy the GirlsThatScuba SMB you can do that here).
About the author
Simon Lorenz is an award winning photographer, PADI instructor and TDI tech diver. He is the founder of Insider Divers and leads many of our trips.
With Insider Divers he aims to create bespoke trips that get the best possible dive experience for groups of fun like-minded divers.
Read more about Simon here