(Tank bangers, BTW, are useless because they always get left behind on the empty tanks. I learned that one the hard way.)
IMO - tank bangers are useless because they get overused ... and eventually people tune them out in self-defense.
What g1138 is referring to is awareness ... and in scuba diving, it's a developed skill, but one that often doesn't get emphasized sufficiently.
Our primary feedback loop for knowing what's going on around us is our vision. Put someone on scuba gear and put them underwater and not only does distance get limited, but placing a scuba mask on your face also removed your peripheral vision ... and so in order to see what you're used to seeing you have to learn a new behavior ... that of turning your head from side to side in order to see what you're used to seeing in your peripheral vision. People only learn this behavior if they're told they need to learn it ... and even then, because we're not used to it, we frequently compensate by "assuming" ... that our buddy is where we expect them to be, for example. Tank bangers aren't necessary for the diver who has developed the habit of looking around, and periodically establishing eye contact with their dive buddy. Nor are they needed for the dive buddy who "swims to be seen" ... in other words, positioning yourself in a manner that allows your buddy to see you easily by simply turning their head in your direction. Tank bangers are a substitute for skills that divers have either never been introduced to, or have decided aren't important enough to put effort into developing.
Communication relies less on equipment than it does on technique and attitude ... the latter being to think of the dive as "our" dive rather than "my" dive. That attitude establishes the basis for a buddy relationship, and makes learning and applying buddy skills possible ... not to mention significantly less effort. Granted, it's an acquired skill ... which means that the new diver should not be expected to have achieved it to a high degree, just as they are not expected to have developed their other skills to a high degree. But they should have established, as part of their basic training, the means by which to learn and hone the skill through repeated application during dives. Relying on lights and tank bangers reduces the motivation to learn these skills ... which can serve you reasonable under certain conditions, but always come with a price. In many instances, the price is simply that you won't be motivated to improve your skills because you have a substitute that serves the need. But when the substitute either fails or is inappropriate to the circumstances, you then don't have the skills to fall back on.
Your eyes, behavior, and brain will do far more for you than bangers and lights ever will ... because they're adaptable to an almost infinite variation of circumstances, while the equipment is only applicable to certain types of diving. Sure, it's more effort ... but so was learning how to walk, and look at how much thought you put into doing that these days. Equipment should always be viewed as an enhancement to your skills ... not a substitute for them. Good buddy skills are perhaps the most important skills you can learn as a new diver, and unfortunately, one of the most overlooked in a significant percentage of OW classes.
... Bob (Grateful Diver)
