Editorial

By Alex Brylske Photo by Joseph C. Dovala

On Visibility And Vision

This month's cover feature addresses what's without a doubt one of the most important features of any dive: visibility. In fact, it's such a common and vital concern that we normally don't even use the full term, referring to it most often as simply "viz." When compared with life on terra firma, the underwater world is generally quiet and, in most cases, speech is impossible or ineffective. Smell, of course, is out of the question, and taste, well, yuck. This adds up to making the diving experience one that's dominated by vision over all other senses. So, with due deference to the few blind divers out there, a dive with zero visibility is pretty much pointless.
As we learned in our scuba class, visibility is determined by two factors that affect the behavior of light as it passes through water: absorption and scattering. Absorption deals with water's innate ability to eliminate light selectively as a function of depth, making most of the ocean — the part down deep that we never see — a black void. The other aspect has to do with the amount of particulate matter in the water column. It's what we formally call turbidity. In other words, some of the light never gets very far underwater, and some that does make it down there is dispersed in such a way that it makes things look dim or blurred. But that's only the physics of visibility.
In addition to its literal meaning, I believe there's also a figurative form of underwater visibility, and it has absolutely nothing to do with physics. The term visibility implies the concept of vision, and Webster defines vision in two ways. It's either "the faculty or state of being able to see" or, more figuratively, "the ability to think about or plan the future with imagination or wisdom." It's the latter definition that I'm talking about. Note the operative terms "planning" and "wisdom." In diving, these are two key concepts necessary to coming back alive.
Using an analogy to extend the definition, you could look at the "light that doesn't arrive" as a lack of training, and the "light that gets dispersed" as the lack of experience. To use yet another analogy, it's like getting a bit rusty. What this really means is that true underwater vision involves more than just seeing. It requires you to have the requisite knowledge and experience to interpret what's before you in a way that you understand and will keep you safe. And that can happen only if you're well-trained and keep both your knowledge and skills in tune. So, keep that figurative definition in mind the next time someone asks you, "How's the viz?"