Training Fundamentals: Best Surface Signaling Devices for Divers

Surface signaling devices are an essential piece of diving equipment. In what circumstances might you use one and what options are available?

Many agencies’ beginner-level scuba courses now introduce surface signaling devices to new divers — and rightly so. A surface signaling device is a vital piece of equipment for all divers, for both logistical and safety reasons. In what circumstances would you use one, and what options are available?

Why might you need a surface signaling device?

Within the confines of a swimming pool during training, a surface signaling device may seem silly. However, when your diving moves to an open-water environment, a good surface signaling device may help you maintain contact with the dive boat or shore, mark your location, or — in the worst-case scenario — help you signal for assistance or rescue when in distress.

There are multiple scenarios when you might use a surface signaling device. Some of the most common are:

  • Marking your location on the surface for boat traffic at busy dive sites to ensure you’re clearly visible to vessels moving in the area
  • Signaling to the boat or shore to let them know where you’ve surfaced at the end of a drift dive so they know where to pick you up
  • Signaling your location in the event that you become lost or separated from the group and surface in an unexpected area
  • Signaling for assistance in case of an emergency or rescue situation when a member of the dive team requires urgent medical attention

It’s important to note that some signaling devices are meant to notify others of your location, whereas others are to be used only in an emergency situation.

Most introductory dive training courses recommended that each diver carries a minimum of one audible and one visual surface signaling device. But what does this mean? We often break down the categories in three main ways: audible, visual and electronic.


Every diver has an in-built audible signaling device: their voice. In an emergency, yelling loudly for help is an instinctive and sometimes effective option if your hands are occupied and you need to raise an alarm. In calmer conditions or over a small distance, calling for help may work. However, over a considerable distance at sea, in wind and waves, or over the rumble of a boat’s diesel engine, a diver calling for help is unlikely to be heard.

Many jackets, wings and snorkels have a simple whistle built into them. Divers can also buy a whistle separately as an accessory. While seemingly very low-tech, a whistle’s high-pitched sound can carry over a greater distance than a human voice. Accounting for the small financial outlay, a whistle is an inexpensive and effective audible signaling device to carry as part of your standard equipment.

The loudest commonly available audible signaling device is the air horn. You’ll usually connect this device to the low-pressure hose of your regulator and, at the press of a button, it emits a very loud blast. Air horns don’t need batteries or charging before use and with prices beginning at $40 USD, they’re relatively inexpensive too. You can hear some of the more-effective air horns over distances of up to 0.5 miles (0.8 km), which means rescuers or boat crew may be able to hear you even when visual signals are ineffectual due to poor light, waves or foggy conditions.

Although it doesn’t need batteries, the air horn’s main drawback is that it is powered by the gas from your tank. Therefore, in the event of an out-of-air emergency, the air horn is powerless.

Visual signaling devices

Every beginning diver learns not to wave their arms around in the air at the surface unless there is a genuine emergency. Much like shouting for help, a waving arm is the most basic and instinctive form of visual surface signaling that — regardless of where you are in the world — notifies other divers and surface crew that you need help. In calm conditions and at close quarters, waving your arms may be successful. However, at a distance, in waves or in poor light, doing so is not useful or effective.

Aside from other devices on this list, the next logical visual signaling device is your fin. Removing a fin and waving it above your head creates extra height that may make you visible in rolling waves or at a greater distance. However, with an average set of fins weighing 5 to 6 pounds (2-3 kg), waving one above your head is not only tiring, but wearing only one also compromises your movement in the water. And, if your fins are not brightly colored, they may not be easily visible to onlookers.

Alternately, signal mirrors are inexpensive, easily available, and you can use one signal the boat or shore from a significant distance. If you’re on a tight budget, you can even stash an old CD in your BCD pocket for emergencies. Of course, a mirrored surface is only useful in bright weather and is useless in low light, fog, or on a night dive.

For night dives and poor visibility, artificial light is the best option. Carrying an underwater light and a backup light means you’ll not only be able to light your path through the water, but also have a way to signal the boat or shore at the surface. You can also use your torch to light up a surface marker buoy to give it a bright glow by holding the light close to the SMB, or inside the SMB on open-ended versions.

In addition, many modern lights feature an SOS setting that signals the distress call in morse code. LED strobes that emit a blinking light are also very useful; not only are they effective in keeping groups together in low-visibility and night-diving conditions, but they also flag your position until safely back on dry land.

The most common, and essential, surface signaling device is the surface marker buoy, also called a safety sausage or SMB. Available in a range of sizes and options, this long tube is often colored orange and you can inflate it orally by using your alternate-air source or with your LPI hose depending on the model. SMBs are often larger, better constructed and have more features as you move up through the price increments; some even have reflective strips or strobes. Larger SMBs may be up to 10 feet (3 m) long.

Your choice of SMB will usually depend on where you want to store it on your equipment during the dive, whether you will be traveling and, most importantly, the conditions in which you will be diving. Of course, the more volatile or challenging the conditions — and greater the wave height — the more substantial the SMB should be in order to be seen.

Electronic signaling devices

Technology has made giant strides and, since dive computers first appeared in the early 1980s, they have now become as ubiquitous and advanced as iPhones. Many modern dive computers now include GPS tracking which, while not a surface signaling device, allows divers to track entry and exit points and location more accurately.

In addition, this system has been used to create GPS markers such as the Nautilus Lifeline. This computer-sized device stays in a housing and a diver may store it in their BCD pocket or attach it to their equipment. Using the latest technology, it allows the diver on the surface to either use VHF radio to communicate or, in a more serious emergency, to press a red button to send their GPS location (within a few feet/meters accuracy) to the Coast Guard or any boat within 4,000 square miles.

Many liveaboard vessels in challenging locations now routinely distribute these GPS markers to their guests, who pay a deposit for the item during the duration of their diving.

Whether audible, visual or electronic, surface signaling devices are an essential piece of equipment. Every diver should have the correct tools to communicate at the surface for comfort and safety, and what you purchase and choose to use will depend on the style and location of diving you’re undertaking. Not sure? Take some advice from your local dive center. In the worst-case scenario, your life may depend on it.