Signaling devices
Signaling devices are important safety tools which scuba divers use to be easily seen or heard underwater or on the surface. There are sound devices used to attract attention and visual devices to mark the location of the diver. Every diver should always have one of each with him to be equipped for different situations.
SMB (Surface Marker Buoy)
SMBs, also called safety sausages, are inflatable tubes, mostly colored in bright red. They can be inflated by the regulator (octopus) and should have a sufficiently long cord.
The longer they are, the better they are visible on the surface, even in swell or waves. The handling of SMBs need a bit of training, to learn the technique to inflate it safely without an unwished ascend (but full enough to stay up on the surface) and without getting entangled in the cord. So it's recommended to do at least one dive with an instructor or dive master who can show you the technique and who is able to assist you if needed.
Safety sausages should be checked before the dives to ensure that they have no holes and that the cord is not tangled up. The best way to avoid entangling is to use an SMB reel.
Dive flag
Floating dive flags are used to warn boats or surfers that divers are down. In some regions they are even required by law. An inflatable buoy carrying the flag is fixed on a cord which is towed by the divers. The floats need to be stable enough not to flip over.
When diving from a boat the dive flag should be distinctly visible on the boat, to announce that there are divers in the area. There are 2 different kinds of dive flags, one is red with a white diagonal stripe, the one other is white and blue (Alpha flag), which are used depending on local regulations.
This is why every diver should be aware of the local requirements in order to carry the recognized flag.
Strobe light
These battery powered strobe lights produce regular flashes of light which are visible in the dark for long distances. They are suitable for underwater use as well and provide a well recognizable signal. If you want to carry a strobe during a night dive to be recognizable for your dive buddy, make sure that this kind of light is not used to mark the diving boat, as this would confuse the other divers in their navigation back to the boat.
Signal mirror
Signal mirrors can be used at the surface, their reflection can be seen even from helicopters.
Whistle
Marine whistles can be attached on the BCD, they carry a long way over water, but the sound of hard wind can reduce their identification.
Buzzer (Alert horn)
Those Buzzers are more effective than the common scuba whistles as they are much louder and work underwater as well. They are attached to the inflator hose of the BCD and therefore powered by the air of the tank.
Tank banger
The tank banger is a very simple device to get your buddy’s attention. It is a bungee strap with a metal or a hard plastic ball, which is attached to the bottom of the tank. This way it is easy to grab. You snap the strap with the ball against the tank. This noise will be clearly recognizable underwater.
