Surface signalling devices are important in just about all diving situations, unless you are doing a shore dive in an area with no real current that you know well. Nobody wants to be stranded out at sea because they lost the rest of their party underwater and emerged far from their boat, or because the boat accidentally left without them.
Equally, if currents carry you away and you are too busy exploring to pay much attention to where you are, you can travel a quite surprising distance. Surface signalling devices can help people find you in these kinds of situations, and can also help you reunite if you get separated from your buddy on the way up.
What Kind of Surface Signalling Devices Are There?
Surface signalling devices for divers fall into two main categories – visual, and audible. Generally you should carry both forms, because they are both more effective in some circumstances than others. Luckily, surface signalling devices for getting noticed both with sound and visual signals are light and easy to find, so you should make sure they are part of your standard dive gear every time you dive.
Audible Surface Signalling Devices
The most basic type of surface signalling device you can get is a whistle. You will probably get one of these even with rented basic dive gear, and it makes sense to carry it. A whistle can be surprisingly effective at getting the attention of people searching for you – the sound can carry as far as half a mile away.
It can also work for you at any time of day or night, unlike a lot of visual aids which require it to either be light or dark. A whistle won't stop working on you either, since it is such a basic thing. The drawback to a whistle is that it can't be heard over a boat's motor, and it is of no use at all if you are trying to signal a rescue helicopter that is looking for you. It also has a limited range.
A more powerful audible surface signalling device is an air horn. These are specially made for divers to use to create loud bursts of sound with the air in their tank. The sound can be heard up to a mile away, though it is still of no use when you are dealing with a helicopter. The other downside is that if you have no air in your tank, you can't use it. If you have an air horn, still carry a whistle as a back up for this very reason!
Visible Surface Signalling Devices
The easiest visible signalling device you can carry is a [signal mirror] (http://www.dougritter.com/psp_rescueflash.htm). This is very effective for signalling both boats and helicopters, provided you have seen them first to signal at them. It works in any daylight conditions (though less powerfully if it is cloudy), and is of course never going to run out of power. The downside is it is no good to you at night. An easy and cheap option is to have a good old CD attached in one of the pockets of your BCD. Make sure to check it once in a while because the salt water can deteriorate the shiny layer of the CD. For our younger readers who do not know what a CD (compact disc) you might want to read more [here] (http://en.wikipedia.org/wiki/Compact_disc)
How Big is your sausage?
Another thing you can carry is a “safety sausage”, or SMB (surface marker buoy) This is an inflatable device that sits upright on the surface once you inflate it using air from your tank, making you far more visible. It is brightly coloured and, provided strong winds don't stop it standing up, very easy to spot. Again, it doesn't help you at night, when audible signals will be more effective, and also will not inflate if your tank is empty when you surface.
GPS & Radio
Last but not least there is a fairly new signaling device available called the Nautilus life line.This waterproof GPS transmitter can be used to send a signal as soon as you need help when you are stranded in the water.
Can you imagine being left in the water and you are drifting in open water? It happened before and it will happen again. When you find yourself in this situation a basic surface signaling device will not do the trick. As soon as you enable The Nautilus life it will start sending you GPS coordinates and your are able to radio for help.
This is when you need to radio for help and that is what the Nautilus life line can do. This device is not only suitable for divers but for Divers, Surfers, Paddlers and Sailors too.