Sorry, I did not intend for this critique to be this long, but I felt the explanation was necessary for the critique to be valid. However, as I have not been able to come up with anything that would benefit the poem, you may wish to by-pass the critique entirely.
When something can mean anything, it means nothing.
Physical: since there is less light below the surface the darkness is a given, as the intervening medium blocks it off from the observer. So on the physical level it is simply a statement of fact. At the psychological level it would generally refer to the unconscious, specifically to hidden motivation, the ones we keep hidden even from ourselves, or anything else we are unaware of in our own psyche. This could also extend to such things as Jung's "collective unconscious" (shared archetypes as language), or Stanislaw Groff's accessible DNA. These are mainly "dark" because they are hidden or unknown to us. There is the corporate level, which includes governments, religions, and business. It is often referred to as the dark underbelly of business. It is something to the effect of a shoes company who spends a fair amount of money each year to give thousands of poor children free shoes (usually seconds, and tax deductible) while at the same time using labor of similarly aged kids who are paid starvation wages to make the companies shoes (this is where it begins to begin to be associated with evil). It could also apply to many other situation. That it has been applied to such a large extent and for so long it is a bit of a cliche depending on how it is used. You used another cliche, the trees forest one. What I see is this generates and keeps generating trees, that soon I am surrounded by a forest. Sorry, but I just don't see this as being a profitable way to go. That's my take on it today hopefully I am in error, nothing would please me more.
Dale
How long after picking up the brush, the first masterpiece?
The goal is not to obfuscate that which is clear, but make clear that which isn't.