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Surface Marker Buoys (SMBs)

Being able to let the surface know where you are during a dive is critical in some situations, and highly recommended in most others. The main ways divers use to achieve this are: a Surface Marker Buoy (SMB) which stays on the surface, with or without a dive flag; a Delayed Surface Marker Buoy (DSMB) which can be deployed by the diver from underwater; or a Safety Sausage which can only be deployed on the surface.

We consider the Safety Sausage to be unsafe and don't sell them. After all, how do you safely get to the surface in areas where there is boat traffic in order to deploy your safety sausage. They are usually much smaller than DSMBs, and thus don't do nearly as good a job as a signalling/location device.

Most people refer to a DSMB as just a SMB, which is why this category is called Surface Marker Buoys (SMBs), but technically they're very different.


A Surface Marker Buoy (SMB) is floated on the surface during a dive to mark the diver's position during drift dives, night dives, mist or disturbed sea conditions. A SMB is absolutely essential kit for diving anywhere you may have surface boat traffic. It allows your position to be known by people watching from shore and watercraft, whether they be the boat you are diving from, or other water users. Typically a SMB will have a dive flag on it as well. See Surface Markers for our range of SMBs.

A Delayed Surface Marker Buoy (DSMB), decompression buoy or deco buoy, is deployed whilst the diver is submerged and generally only towards the end of the dive. The DSMB marks the diver's position underwater so the boat safety cover can locate the diver even though the diver may have drifted some distance from the dive site while doing safety or decompression stops. A reel or finger spool and line connect the buoy on the surface to the diver beneath the surface.

Our recommendation is that all divers should carry a DSMB and reel on every dive. In many boat diving situations it's also good practice to also have a Surface Marker with dive flag up on the surface to tell your surface support where you are for the whole of the dive.

SMBs and DSMBs are not intended to be used to lift heavy weights. That's what a Lift Bag is for.

Where to Deploy Your DSMB

Delayed SMBs, such as the AP Diving Buddy DSMB, are designed to be deployed from depth near the end of, or at any critical point during, a dive. Some divers, like us, prefer to shoot their Delayed SMBs from the bottom and thus let the surface support know they're begining their ascent. Other divers shoot from mid-water when they start their safety stop, or decompression stops. We strongly recommend you have a Delayed SMB and reel/spool with you on every dive. On open water dives, waiting until you surface to deploy a surface only safety sausage is dangerous in high boat traffic areas.

Which Colour Delayed SMB Should you Use

There are essentially three choices for DSMB colouring — all Red, all Yellow, or Red and Yellow on contrasting sides.

Studies have shown that Red and Yellow are the two most visible colours at sea. But each colour works better than the other in different conditions. Thus if you look around a dive shop, you will see up to three SMB colours: all Red; all Yellow; and one side Red, one side Yellow.

Recreational Diving

An all Red SMB is far and away the most common SMB colour. This leads some new divers to buy an all Yellow SMB so theirs will stand out more when at a busy dive site. We don't recommend this.

Other divers buy the two-colour SMBs (Red on one side, Yellow on the other side) because these must surely be the ideal for high-visibility over the widest range of conditions. For recreational diving, especially when ocean diving, this is what we recommend. However, it is essential that you let your surface cover know that your combined Red and Yellow SMB is not being used as an emergency signal unless an emergency signal or message is attached to it.

Advanced/Technical Diving

In Australia, and many other parts of the world, there is a convention used by more advanced and technical divers that an all Yellow SMB is an emergency signal, to be responded to by sending down a cylinder of gas, or a rescue diver, or both.

Whilst for the most part recreational divers do not have or need such a signal, it is possible for both types of diver to be on the same dive site. If one group of divers is using Yellow as an emergency signal and the other group uses Yellow as standard, this could lead to confusion and even to a genuine emergency signal being ignored.

For this reason, unless you have a very strong reason for wanting an all Yellow SMB as standard, please don't buy one.

If you decide that you would like to use a Yellow SMB as an emergency signal yourself, two precautions to take are:

  • Make sure your surface cover knows this convention
  • Mark the SMB with "EMERGENCY", "HELP", "SOS" or some other such message in large, clear black letters to ensure there is no doubt that you are a diver in distress and not just a diver who thought a Yellow SMB looked nicer than a Red one.

Boat Diving Safety

Boat Diving Safety

When Lloyd Borrett set up his private dive boat for Melbourne diving in 2011, he added to his existing knowledge and researched the local best practices, taking a close look at what others were doing (especially the VSAG independent dive club), and came up with the following setup. It worked for him, maybe it will work for you just as well.

You should also take a look at Using a Dive Float and Flag which describes how to use a dive float and flag for additional safety in diving.

Diving Flag Alpha

For the purposes of diving operations the vessel should carry a replica of the international Code Flag 'A' flag. This should be capable of being displayed fully extended preferably rigid and should be as large as possible. It should be displayed at all times that divers are in the water. It must not be displayed once all divers have been recovered.

Diver Below Signals
Diver Below Signals
The rules governing the use of a dive float and dive flag vary by state and locality.

Diver Below Flag: In Victoria, any vessel with divers operating from it must always display signals by day or night to inform other vessel users. The daytime diver below signal is the international Code Flag 'A', at least 750 mm long and 600 mm wide for vessels less than 10 metres in length. For vessels longer than 10 metres, the dive flag must be at least 1 metre long and wide. It should be placed to ensure all-round visibility.

Diver Below Lights: During night diving, a vessel must show the international signal for a 'vessel restricted in its ability to manoeuvre'. These are three lights in a vertical line, top and bottom are red and the middle one is white.

In Victoria, a five knot (9.3 kph) speed limit applies to vessel operators and water-skiers within a distance of 100 metres (328 feet) of a vessel or buoy on which a 'diver below' signal is displayed.

Please note that the dive flag does not mean that other vessels can't come up to and right past the dive flag, or any vessel displaying a dive flag. There is no 'exclusion zone' — just a speed restriction zone.

Predator Plastic Alpha Dive Flag - Large Predator Plastic Alpha Dive Flag - Large
RRP: $30, Our Price: $21, You Save $9 (30%).
This 750 mm by 600 mm size flag meets the minimum requirements in Victoria for a boat less than 10 metres long. We attach it to a long wooden broom handle and put it into a convenient rod holder.

Boat Lines, Shot Lines, Drift Lines, Cray Lines, Decompression Trapese etc.

To cover the requirements of running the boat, beach launching, plus doing various types of diving, an assortment of lines and buoys are used.

The 10 mm and 12 mm white nylon 3 strand rope, the yellow 10 mm ski rope, plus the 6, 8 and 12 mm stainless steel, asymmetric snaps, described here were purchased from Quarterdeck Marine, in Seaford Victoria.

To label various lines, Lloyd purchased a Mills Styrox SPS 33 Business Hours sign from Bunnings. This 200 mm x 300 mm sign can be cut up into eight 66 mm x 100 mm tags, drilled to create the appropriate sized hole, labeled on one side with a Sharpie Permanent Marker, and attached to lines with cable ties.

Boat Lines

Long Dock/Tow Line: A Blueline Dock Line, 12 mm double braided nylon, 30 metres long, with a soft eye spliced in one end gives excellent shock absorption and abrasive resistance. Purchased from BCF, Braeside Victoria.

Shorter Dock/Tethering Line: A Blueline Dock Line, 10 mm double braided nylon, 4.5 metres long, with a soft eye spliced in one end gives excellent shock absorption and abrasive resistance when used as a dock/mooring line. Purchased from BCF, Braeside Victoria.

Short Dock/Tethering Line: A Blueline Dock Line, 10mm double braided nylon, 3 metres long, with a soft eye spliced in one end gives excellent shock absorption and abrasive resistance. Purchased from BCF, Braeside Victoria.

Main Marker Buoy for Shot, Drift and Cray Lines

The Marker Buoy should be a bright colour and easily visible in the sea conditions expected. It must be of a suitable size for the diving taking place and have sufficient buoyancy to support any divers or equipment that may be used for decompression. A minimum of 20 kg is recommended for this purpose. Under no circumstances should the buoyancy of the marker buoy be less than the shot weight. Sufficient line must be used taking into account tidal variation during the diving operation.

The main marker buoy Lloyd used is a pear shaped, DAN-FENDER Inflatable heavy duty buoy, injection moulded from tough flexible orange vinyl (model B50). Purchased from Anchor Marine, Sandringham Victoria. It features a heavy duty black solid injection moulded eye, high gloss body and metal inflation valve. It has an overall length of 570 mm, 405 mm in diameter, with an eye diameter of 28 mm and a buoyancy of 46 kg.

A 1 metre length of 12 mm white nylon 3 strand rope, is used to secure a 12 mm stainless steel, asymmetric snap hook to the main buoy. The snap has a formed eye and strong spring opening action. The rope is securely spliced to the buoy's eye at one end and to the snap hook at the other end.

Dive Marker Buoy
Dive Marker Buoy

Shot Lines and Weight

Diving with Shot Lines
Diving with Shot Lines

A simple shot line will consist of a shot weight, a suitable length of line and a marker buoy.

This equipment needs to be versatile for the various depths of water being dived and suitable for the type of diving being undertaken. A shot should be at least 15 kg if the position is to be marked in tidal waters. The line should not be too thin as this results in handling and recovery difficulties. A shot line diameter of at least 10 mm is recommended.

Lloyd setup three shot lines from 10 mm white nylon 3 strand rope. They are 40, 20 and 10 metres in length, which enables him to make up the various length combinations required for the range of dive sites we use shot lines on.

Each line has an 8 mm stainless steel, asymmetric snap hook securely spliced onto each end. These snaps have a formed eye and strong spring opening action.

Shot lines
Shot lines

Lloyd used nylon line because it's nearly twice as strong as silver rope. This allows a smaller diameter rope to be used which proves cost effective. Nylon rope is the strongest and most elastic synthetic fibre UV resistant rope. It is easy to handle, has great elasticity, shock absorption and abrasion resistance, plus it can be cleaned easily in soapy water.

Tidal Indicator Pip/Buoy Line

Tidal Indicator Pip/Buoy Line
Tidal Indicator Pip/Buoy Line

To help determine what the tidal current is doing when waiting for slack water, we have a tidal indicator pip/buoy line. This uses three white solid styrene surface floats — a 150 mm diameter float at the far end, then 1 metre apart is a 120 mm diameter float, then another 1 metre apart is a 100 mm diameter float.

About 1 metre from the smallest of the floats a 8 mm stainless steel, asymmetric snap is securely spliced onto the end of the line, which is used to clip the line to the main buoy. The line used is yellow 10 mm ski rope.

Pip buoy line
Pip buoy line

Cray/Drift Buoy Lines

Dive Buoy Lines and Boat Dive Flag
Diver Freedom System: Dive Buoy Lines and Boat Dive Flag

The main buoy is deployed. Clipped to it is a 20 metre length of yellow 10 mm ski rope with 8 mm stainless steel, asymmetric snaps securely spliced onto each end.

A 1 metre long short float line made from yellow 10 mm ski rope, with a 100 mm diameter, white, solid styrene surface float in the middle, plus 8 mm stainless steel, asymmetric snaps securely spliced at each end, is then attached to the end of the first line. This keeps the line up in the water column so as to help the line from being snagged on reefs.

For each diver, a 12 metre length of yellow 10 mm ski rope with 8 mm stainless steel, asymmetric snaps securely spliced at each end, is clipped to the end of the short float line. There is a small stainless steel snap positioned in the line 3 metres from the end, to which a long cray snare can be attached when cray hunting in South Australia.

Drift/cray dive lines and float line
Drift/cray dive lines and float line

For drift dives, a 250 mm long, 25 mm diameter, wooden handle — one per diver — is clipped to the end of each of the 12 metre drift/cray lines. The line is a length of yellow 10 mm ski rope with 8 mm stainless steel, asymmetric snaps securely spliced into the end.

Drift dive handles
Drift dive handles

For cray dives, a reef pick (reef anchor with just two 8 mm prongs) is clipped to the end of the 12 metre drift/cray lines. The reef anchors are hot dip galvanised, but they have also been painted with two coats of White Knight Rust Guard Cold Gal zinc rich coating for lasting protection, plus two coats of White Knight Rust Guard Yellow Epoxy Enamel.

Reef picks
Reef picks

ex HMAS Canberra Safety Line

When diving the ex HMAS Canberra, we tie up to a mooring buoy. We then drop a line down from the boat with a 5 kg lead drop weight such that it hangs 5 metres below the boat. The line has stainless steel snaps at each end. The weight has eye loops top and bottom.

A 30 metre length of Grunt 9mm braided, solid core, multi-purpose yellow colour rope (part # GR0003) purchased from Bunnings, with stainless steel snaps at each end and a small 100 mm diameter white solid styrene surface float attached one metre from the far end, is clipped to the bottom of the drop weight.

The far end is then taken by the first diver down to the wreck. A wire coat hanger is used to attach the line to the wreck. The last diver to start the return journey can easily detach the line from the wreck. Even if they fail to do so, a strong pull from the surface will detach the line.

Diver Recall Signals

Consideration should be given on all vessels to provide a suitable means of recalling divers should the need arise. Whatever method is adopted divers must be clearly briefed on what to expect and what action to take in the event of such a signal being deployed.

There are a number of methods of recalling divers, alerting them to abort the dive for safety reasons:

Improvised Methods

  • Tugging on Surface Marker Buoys (SMBs)
    – Usual practice is four strong tugs
  • Sending disc down an SMB line
    – Negatively buoyant plastic disc attached to the SMB line by the boat cover to slide down to diver
    – Alternatively to above – dropping a strobe down the line
  • Revving boat engine
    – If no other method available, go near to divers' position and rev boat engines repeatedly in neutral
    Note: Divers might interpret this to mean cover boat getting impatient.

Other References

The Dive Boat Related files on our Diving and Snorkelling Downloads web page are valuable references that will help you to better setup your boat for diving, and help you to conduct safe diving operations.

See also, Boat Diver Safety Briefings.


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