How to use a Surface Marker Buoy

Surface marker buoy (SMB) use is one of the most important, yet under-practiced skills a diver can master. To emphasize it’s importance, it was added to the PADI Open Water Course curriculum in 2015. If you were certified before 2015, you may never have learned to use an SMB, so here are some tips to get you started. Remember, practice with an instructor or experienced dive buddy before releasing a buoy for the first time on your own.

Why deploy an SMB?

Although not deployed on every dive, there are still a variety of reasons to release a surface marker buoy. It may be necessary to swim with an SMB during an entire drift dive so that your surface support can easily track your progress. It may be essential to release a buoy at the end of a dive to alert watercraft to your presence before ascending (especially important in areas with boat traffic). In addition, the line attached to your SMB may be used as a reference point for a controlled ascent. Finally, many technical divers carry two SMBs of different colors; one to signal surface support that the dive is going as planned and the other to request assistance.

SMB Release Can Be Dangerous If You Don’t Know What You’re Doing

Releasing a surface marker buoy when appropriate undoubtedly improves diver safety, but it can endanger a diver when done incorrectly. Divers risk an uncontrolled, rapid ascent; entanglement; and even injury if the line becomes twisted around a finger or a hand. It’s important to release your SMB in a controlled and safe manner, and to practice the skill repeatedly in easy conditions to develop muscle memory and make the process smooth and efficient.

How to Release a Surface Marker Buoy Without Getting Into Trouble:


Select an SMB appropriate to your dive conditions. If you are unsure what kind of SMB to use, research surface marker buoy styles and features, and chat with local divers about their SMB of choice and what other surface signaling devices they carry. In addition, reel/spool choice is important, and the most popular option is a solid, negatively buoyant spool that is attached to the diver with a double-ended clip when not in use. It’s important to have enough line on your reel or spool to deploy an SMB at your planned depth, and to use braided nylon line.

Choose Your Deployment Depth

It’s best to deploy the spool as early as is safe during the ascent. Doing so allows the diver to add only a small amount of air to the buoy because the air trapped inside the buoy will expand during ascent, resulting in a fully inflated buoy at the surface. The deeper you are when you inflate it, the more the air in the buoy will expand as it rises to the surface. Conversely, the less you have to inflate the buoy under water, the easier it will be to maintain buoyancy during the inflation process.

Signal Your Buddies

Communicate to your dive team that you intend to release the buoy. This will help to avoid entangling them in the line, and will ensure that they are ready to assist you should you encounter a problem. Your buddy should deploy a line cutter and be ready to cut the line in a worst-case scenario.

Establish Neutral Buoyancy

Once you have your hands busy with the buoy, it’s going to be difficult to adjust your buoyancy. Take your time to establish stable neutral buoyancy before releasing your buoy so that you can focus on releasing the buoy without worrying about your basic dive skills.

Position Your Self Properly

If there is a current, turn your back to it so that when you release the buoy, it will drift downstream away from you. This will make handling the buoy easier and avoid entanglement. In addition, be sure to look around, especially above, to be certain you will not release the buoy into another diver, under the boat, or in a way that it will impact the reef.

Deploy the Surface Marker Buoy and Spool

Unclip the spool from your harness or BCD, remove the clip and secure it to a d-ring, and attach the spool to the SMB if necessary. Take a moment to check the line on the spool to confirm that it is not snarled and that there is no loose line.

Inflate the Surface Marker Buoy

Open the bottom of the surface marker buoy and hold it above your regulator exhaust valve (where the bubbles come out when you exhale). Breathe out a few times until the buoy partially inflates and tugs upwards on your hands, but avoid adding so much air that you cannot maintain buoyancy. In the case of a SMB that must be orally inflated, partially fill the SMB with a breath or two. However, these sorts of SMBs are not recommended.

Unspool a Bit of Line

Allow the spool to unwind a few feet, and look over the spool to make sure the line is not entangled. Check one more time above you for other divers and obstructions to make sure the SMB has a clear path to the surface.

Release the Buoy

If the situation looks under control, allow the spool to unwind and the SMB to rise to the surface. If the spool starts to pull you to the surface, drop it. It’s more important to maintain a proper ascent rate than to keep hold of your spool, and you will mostly likely be able to retrieve the spool as it unwinds and drops back down (this is one of the reason’s it’s nice to have a negatively buoyant spool). If you become entangled, you or your buddy should immediate cut the line. A replacement buoy is much cheaper than a trip to the hyperbaric chamber.

Safely Ascend

Once you have deployed your SMB, it’s likely that your movement will be limited, so choose your location wisely. Consider the direction of the current and wind, and realize that these may drag you along as you hold the SMB. Allow yourself to drift, and if necessary, your buddies may gently hold the line above you to keep the team together. Otherwise, simply ascend together slowly, using the line and the spool as a visual reference. Remember, loose line is your enemy. Keep some tension on the line by winding it up as you ascend. Drifting line can become entangled with itself or with a dive buddy. No diver in the team should turn his back on the line, so ascend face to face with your buddies. Knowing where the line is will prevent an inadvertent entanglement. Finally, during a safety stop or decompression stop, it’s perfectly acceptable to lock your spool or reel to prevent it from unwinding, but never clip it to your body when the buoy is inflated. Keeping a small amount of tension on the locked spool will often help you to maintain depth and buoyancy.

Clean and Dry Your Surface Marker Buoy After Diving

After diving, rinse both the inside and outside of your SMB with fresh water. Inspect the line, and re-wind it if is unevenly or loosely loaded, and periodically grease the moving parts of your clip to avoid corrosion. Dry the SMB in the shade to that it keeps its color and stays highly visible for future dives.

Final Thoughts About Surface Marker Buoy Use

It’s important to master surface marker buoy deployment at any level of diving, as it is valuable safety skill. If you missed out on this during your open water course, grab a buddy or an instructor and start practicing. Learning new skills is fun, and this skill just might save your life one day.