Underwater Signaling Devices?

[Jeddah Aquanaut]

I use a Sub Duck, and it works just fine. It is possible for your buddy to recognize it is you (instead of the [often] 1/2 dozen other divers with the same device). Just work out a distinctive signal, not just a long quaaaaaaaaaaaaaaaaaaaack. If I am on the surface and so far away that no one can hear it, then I've got my tall sausage, and an old CD for flashing.

The hammerhead only works underwater. The Scub quacks underwater, and also makes a fairly loud noise above the water. I believe the older models (sub-alerts or sub-ducks) are not as effective on the surface as the sCub alerts.

And for the record and somewhat in reply to the original post, I agree that good buddy communication is vital, but I do feel a noisemaker is nice insurance.
By the way, the butt of the knife on the tank works pretty well, but didn't carry as far as my buddy's sub alert (I could hear him, he couldn't hear me when we tested the methods).

Jeff