- What Is An SMB
- What Is An DSMB?
- Why Do You Need An SMB
- Best SMBs
- How To Choose An SMB
- How To Deploy An SMB
An SMB, or surface marker buoy, is the one scuba diving accessory that no responsible scuba diver should ever dive without.
When it comes to safe scuba diving practices, an SMB is an essential piece of dive gear.
Yet many new, and even some experienced divers, often forget about the SMB and why it’s important to have an SMB when you go scuba diving.
Here at ScubaOtter, we care about your safety. And that’s why we’ve put together a guide on everything you need to know about SMBs for scuba diving.
In this article, we’ll be covering why you need an SMB, how to choose the best SMB, and a run-down of the best SMBs on the market.
Plus we’ll be sharing our tips on how to deploy an SMB and DSMB.
So let’s get started.
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What is an SMB?
SMB stands for surface marker buoy. An SMB is a simple inflatable device that floats on the surface to mark the position of scuba divers. This allows people at the surface to keep track of the divers and lets boats know to stay away.
Typically a surface marker buoy is inflated at the beginning of the dive and towed along by the diver. An SMB can also be inflated at the end of the dive to signal the dive boat to come to pick up the divers.
SMBs can be round or a long tube shape. They are always brightly colored making them easy to spot, even in rough conditions.
What is a DSMB?
A DSMB, or delayed surface marker buoy, is a type of surface marker buoy that divers inflate underwater and release to the surface prior to ascending. Hence the term ‘delayed’.
You may also hear divers fondly refer to their DSMB as a safety sausage due to its long, round shape.
Why do you need an SMB?
This is the most common question when it comes to surface marker buoys. Here are the reasons why you need an SMB for scuba diving:
An SMB allows you to mark the area where you will ascend.
This alerts any boats in the area that there are divers just below the surface so they can maintain a safe distance. Ascending without an SMB puts you at risk of being injured by passing boat traffic.
An SMB provides a visual reference on the surface.
This ensures that your dive boat can find and helps you to attract attention if you’re lost at sea or an accident happens. It’s much easier to spot a big, bright SMB on the surface than a divers wet head, especially in bad weather.
An SMB can act as an additional flotation device for a tired or panicked diver.
If the boat is not in sight and you have to wait a long time at the surface, an SMB can provide additional support and a great sense of security.
A DSMB provides a useful reference for the depth and location of your safety stop.
When drift diving, it’s not uncommon to have to complete your safety stop in the blue. Here, a DSMB helps you maintain a steady depth and allows the boat to follow your movement. What’s more, the line of the DSMB provides a handy visual reference, ensuring a slow and steady ascent.
But Do I really need my own SMB?
So you might be thinking…
‘The dive guide always has an SMB, so I don’t need my own’
While it’s true that your divemaster or guide should always carry an SMB with them, it’s still highly recommended that you have your own surface marker buoy.
And here’s why…
Having your own SMB means you can always take care of your own safety.
Perhaps you and your dive buddy want to explore an area away from the main group. There are many dive destinations and liveaboards that allow more experienced divers to dive without a guide. Having your own SMB provides you with much more freedom underwater.
But even if you’re not planning to venture away from your guide there are still situations where you may need an SMB. And where not having one could easily turn a common situation into an emergency.
For example, what happens if you lose your dive guide and have to ascend without them?
Losing your guide is not necessarily an emergency in itself. But without an SMB you have no way of alerting boat traffic as you ascend, or attracting attention at the surface. Both of which could result in an accident.
And even if your dive buddy always carries an SMB. What happens if you lose your buddy and the group?
An SMB is vital if you have to ascend by yourself. Ultimately, this is the reason why every scuba diver should have their own SMB.
Some divers may argue that in this situation they can use their alternate air source to blow bubbles to mark the surface. But seriously, have you tried spotting a divers’ bubbles in choppy conditions?
An experienced captain might be able to. But often it’s impossible. And other marine traffic will definitely not be able to see you.
What’s more, many dive operators and liveaboards now require all divers to have their own SMB.
An SMB is a very small and relatively inexpensive addition to your dive gear. Yet it massively enhances your safety. So why take the risk?
Surface marker buoys are not expensive. Plus they’re small and light enough to bring when you travel.
So there’s really no reason not to get your own SMB!
The Best Scuba Diving SMBs
Offering everything you need in one compact yet robust package, the Dive Smart 6ft open-ended SMB is a ScubaOtter favorite.
Made from 210D Nylon with a TPU coating, this SMB is built to last. The Dive Smart SMB features an overpressure valve and weighted bottom, ideal for all dive conditions.
This SMB is easily inflated using either oral inflation or a regulator second stage. The open-end has a one-way airflow system that prevents any air from escaping at the surface. Available in 3 different high visibility colors, all featuring a large reflective band at the top.
What’s more, this SMB comes with a 100ft (30m) reel, double-ended brass clip and it’s own mesh pouch with a velcro locking system.
- Large & highly visible
- 3 different colors available
- Compact all in one DSMB kit
- Durable & long-lasting
- 2 different inflation methods
- Reflective strip & dump valve
- A little pricey
The Seafard SMB is another great choice. Although slightly smaller than the Dive Smart, this SMB is highly visible and extremely robust. It’s lightweight and compact design makes the Seafard SMB an ideal choice for the traveling diver.
Featuring an oral inflation tube, self-sealing open bottom, dump valve and reflective strip, this SMB has everything you need.
Plus this SMB also comes with a corrosion-resistant aluminum reel with 49ft of braided nylon line and a stainless steel double-ended bolt clip.
- High visibility design
- Comes with reel & clip
- Compact & lightweight
- 2 different inflation methods
- A little too small for rough sea conditions
If you’re looking for a big and robust SMB, then the XS Scuba surface marker buoy is a great choice.
When inflated this SMB stands over 7ft tall and has 3 wide reflective strips at the top. Ideal for more challenging dive conditions where you’re concerned about being seen.
The oral inflation tube and large open end make this SMB super easy to inflate both underwater and on the surface.
- Easy to inflate
- Very large & highly visible
- 3 reflective strips
- Robust material
- 2 inflation methods
- Reel & clip not included
- A little bulky
If you’re looking for a basic yet sturdy SMB to take with you on your diving holidays, then look no further than the Scuba Choice SMB.
This close-ended SMB is super lightweight and compact, making it easy to pop into a BCD pocket.
- Compact & lightweight
- Durable material
- A little small
- Oral inflation only
The DiveSmart dive float is the ideal surface marker buoy for both scuba diving and free diving in areas with high boat traffic.
This SMB is easy to set up and provides permanent visibility at the surface. Plus it comes with a 100ft reel and double-ended clip.
- Great value
- Permanent visibility at the surface
- Robust & long lasting
- Cannot be used as a DSMB
How to choose the best SMB for scuba diving
SMBs come in a wide variety of brands, shapes, and sizes. The best SMB for you will depend slightly on your personal preference but ultimately it comes down to the dive environment.
So let’s take a closer look at the different types of SMBs and what to consider when choosing an SMB for scuba diving.
Open-ended vs Closed-ended SMBs
There are two main types of SMBs for scuba diving; open-ended and closed-ended.
An open-ended SMB is open at the bottom. These SMBs can be inflated using your exhalations or your alternate air source.
Open-ended SMBs are very easy to inflate and deflate. However, air tends to escape from the bottom so they often flop over at the surface making them less visible. You can reduce this by pulling down on the line to hold them upright, although some water will still get inside.
The best open-ended SMBs will feature a one-way airflow system. This means that when the SMB is inflated the opening is pinched closed by the air pressure inside. These SMBs are easy to inflate and will always maintain their position on the surface.
Close-ended SMBs are completely sealed all the way around. A close-ended SMB is usually inflated by blowing into a one-way oral inflation tube, although some models can be connected to a low-pressure inflator hose to add air more quickly.
Closed SMBs will always sit upright at the surface but tend to be a little trickier to deploy, especially underwater.
Whichever type of SMB you choose, make sure that it features a dump valve. As the SMB shoots up to the surface the air inside will expand due to the pressure change. A dump valve will allow any excess air to escape, preventing the SMB from bursting.
Shape, color & size
Permanent SMBs are often round, but if you’re looking for a DSMB you want to pick a long, tube shape that will stand tall on the surface. These SMBs can also be easily rolled up and clipped to your gear.
When it comes to color, it’s vital that your SMB stands out against the water. So make sure you choose a brightly colored SMB. Orange or red provides the highest contrast, but fluorescent pink or yellow will also work well.
Having a reflective strip at the top of your SMB is also very useful. This makes you much easier to spot especially in poor visibility or low light.
With regards to size, your SMB should be at least 3ft (1m) in length. But as with many things in life, the bigger the better!
If you’re diving in relatively calm waters with little to no current then a smaller SMB will suffice. However, if there is any chance of waves or currents it’s important to have a large SMB that can easily be spotted even in rough conditions.
SMB Attachments & Accessories
All SMBs require some sort of line so that it doesn’t just drift away at the surface. Some SMBs will come with a 5 – 6m wrapped line, which is just long enough for your safety stop.
However, wrapped lines are very prone to tangling and don’t offer you the opportunity to deploy the SMB from deeper depths if needed. Plus if there are any waves, wind, or current the line will be pulled which means that 5m won’t be long enough.
Most divers prefer to use a reel with their SMB. A reel safely stores the line and greatly reduces the risk of entanglement. A reel with a 65ft (20m) line is recommended for most recreational divers. But you may want to get a longer line for drift or deep diving.
Reels come in many different forms, but remember the simpler the mechanism the less there is to go wrong. A mounted hand reel is recommended if you’re diving in a location with particularly strong currents or challenging surface conditions. However, for most dive locations, a basic finger reel will work well enough.
With a reel, you can deploy your SMB from deeper depths. Not only is this easier as you don’t need to add as much air, but it can also be very useful in alerting boats to your position before you ascend to your safety stop. The line can also be used as a visual reference to guide a slow and steady ascent.
A double-ended clip is used for attaching the DSMB to your gear and preventing the line from unraveling.
How to deploy an SMB
The method for inflating an SMB at the surface will differ slightly depending on the type of SMB you are using.
How to inflate an SMB at the surface:
- Place the mouthpiece of your alternate air source just inside the open end of the SMB.
- Turn the alternate air source upside down and pull the open end of the SMB slightly under the surface.
- Push the purge button on the alternate air source whilst holding the open end of the SMB until it is full.
- Pull the end of SMB down slightly in the water to make it stand tall.
To inflate a close-ended SMB simply blow into the oral inflation tube.
How to inflate an SMB underwater:
Every diver will have a slightly different method, but here are the general steps for deploying a DSMB:
- Make sure that you are neutrally buoyant at around 5m or deeper and check there are no obstructions above or around you.
- Unclip the SMB from your BCD and open it out.
- Optional: Add a tiny amount of air into the SMB so it sits upright. (Use a small tap from your alternate air source or bring the opening of the SMB to the exhaust of your regulator, tilt your head to the side and exhale)
- Unclip the SMB from the reel and store the clip on your BCD.
- Hold the reel so that it can freely spin on an axis created by your finger, or finger and thumb.
- Make sure the line is on the outside of the reel facing away from you and not wrapped around any of your gear.
- Inflate the SMB using 2-3 full exhales or a short blast from your alternate air source
- Let go of the SMB and allow the reel to spin. Remember to watch your dive computer to maintain your depth.
- Once the SMB is at the surface you can wind the line tight around the reel and hold onto the reel until your safety stop is finished.
- Wind the line around the reel as you ascend slowly.
For a close-ended SMB, you would remove your regulator and exhale into the inflation tube. Don’t forget to save a little air to clear your regulator afterward and never hold your breath!
Sounds like a lot to think about? That’s because it is.
Deploying a DSMB correctly will take a few attempts. But once you’ve mastered it you’ll feel much safer and more independent underwater.
We highly recommend you practice in a swimming pool or very shallow water first to avoid the dangers of a rapid ascent.
And if possible, have a dive instructor teach you how to safely inflate an SMB underwater.
Top Tips for deploying an SMB underwater
Start slightly Negative
This helps counteract the positive buoyancy created by the air you add to the SMB. Try exhaling as you inflate the SMB or deflate your BCD slightly before inflating the SMB.
Take your time
Make sure that the SMB and reel are set up properly before you add any air. If you rush it’s much more likely that you will get tangled in the line.
Don’t grip the reel
Remember to allow the reel to freely spin and don’t be afraid to let go of the reel if it gets stuck or is pulling you up.
Many divers will instinctively grip hard on the reel and end up being dragged to the surface. It’s much easier and safer to just let it go. The reel will almost always fall back down to you.
Never clip an inflated DSMB to yourself
If the SMB is accidentally caught by a boat you’ll be pulled up very fast which can lead to decompression illness and other injuries.
Can I rent an SMB?
You might be able to rent an SMB from your dive operator. However, there are many different types of SMB and not all are easy to use. It’s much better to have your own SMB that you are confident in using.
Plus rental SMBs are not always in the best condition and don’t often come with a reel.
So now you understand why an SMB is an essential piece of scuba diving gear. And how to choose the best SMB for your scuba diving adventures.
No matter which surface marker buoy you choose, we guarantee that you’ll feel much safer and more independent with your own SMB.
Alexa Worswick is a PADI and SSI scuba diving Instructor, recreational freediver and freelance copywriter. She first learnt to scuba dive in the UK aged 15 and has since travelled and dived in multiple locations across 3 different continents. After quitting her marketing job in London in 2016, Alexa is now based in Indonesia where she can pursue her passion for the ocean fulltime.