was reflective – and it was perfect.
You should use two dashes to create an em dash, and the wiki will automatically form it into a longer, single dash, like this —. It might only be aesthetic, but right now your em dashes just look like hyphens to me.
semi-clear
I feel like we can come up with a better word to describe the clarity (or lack thereof) of the water. I would vote for "turbid"
something about a deep gash on his thigh that burned in the calm waters around him.
No critique, I just wanted to point out that I liked this phrasing.
z-drugs
Out of curiositiy, can you explain to me what a z-drug is? Is this real and I'm just not familiar with it, or is it something you made up? I'm guessing it's the latter, but I wouldn't wager money on it.
their edges softened by time pushed by the gentle stream
I feel like this would benefit from a conjunction. "their edges softened by time and pushed by the gentle stream." Also, maybe swap stream for current?
sharp, and strong
Get rid of this comma
traced in freezing relief against his skin.
Again, no critique, I just wanted to give my compliments for this.
determined – well, he could be all those things too.
This might work better if you change the em dash to a period, start a new sentence with "well" and change the comma after it to an elipses … "determined. Well… he could be all those things, too."
pulling him in the direction the stream ran.
This is worded a bit awkwardly. Maybe just "pulling him downstream" or "with the current" or something.
His own hands clasped at the surface, grasping blindly for help
Ehh… this is kind of petty semantics, but you can't really "clasp" the surface of water. Maybe "groped for" or "reach for" instead.
The dark thought the reason there was blood in the water
is this possibly missing punctuation? It feels like there should be something after "thought", but I'm unsure, as I was kind of confused by this.
unsuspected
I think this should be unsuspecting, just as it is in the next sentence.
With one swift pull, all of him
I think this reads better without the comma.
under water
This is a compound word, so it's just "underwater"
and to fight against the alien concept
I think this reads better without the particle, so "and fight against the alien concept" but that might just be me.
coughed pond water
But it's river water, right? he wasn't in a pond.