This is a curious photograph... And water is in fact a very interesting subject, but it was already so explored, so much used and done about that is hard to come up with something that is not redundant. But this fraction of time and space you got here is full of mystery and I love that. Not boring at all! But in the same way it appears to be a little obvious.
Abstract photography is the most hard and tough to master, and this is not due technical difficulties but rather because it goes beyond the real of photography per se and enters the world of paint. It's light, yes, drawing with light, but it falls more in the realm of expression with paint and pigment. That expression that is not portraying anything else than an emotion or something of the sort, with non figurative elements. This has to do with what you can convey emotionally and not so much about a message, or a conceptual idea. In that way I don't thing this is so much abstract photography as it is macro photography with movement and a perennial expression of time in a water flow.
We can readily see that this is water frozen but a fast shutter speed, not to fast but fast enough, depending on the focal distance, the distance to the subject and the speed of the flow, it could be between 1/125 to 1/500, so we have a bit of motion blur in the "bottom of the wave" where water speeds up a bit, and we have it totally frozen, or almost totally frozen on the "riff of the wave".
Nature gives us this in every corner, we just have to see it, but seeing it is not an easy task, as this is the most difficult thing for us. To see without seeing. I know I'm going a bit to philosophical but the subject requires it. We could just see colours and shapes but we see a little more, or, to say it correctly, we can interpret more. The patterns that water makes turns what could just be taken as abstract to be figurative. It's the big difference between having a phenomenological approach to reality and having the psychological interpretation that always comes along.
Anyway, in the bottom left side you have a great mix of clean and transparent water, a beautiful reflex on water with smaller frequency waves, a nice shadow of the boulder and reflex again, darker, which draws a patter that could very well be interpreted as malachite if there wasn't more photograph to "see" (interpret) that it's not. On the top left there's a very well textured high key foam a bit out of focus, which is so nice in macro photography. This foam goes all the way to the top right corner, where we can see a rising wall of thin water full of drops reaching out from the convulsion on the bottom right, where we can very well the rocky substance of the boulder.
I know it's a boulder because of your description, it could be something else, and this is where the shot gets to be a little more abstract photography that macro photography. But I'm not sure that your first sentence "(...) I love abstracts in nature (...)" is enough for any one to make the assumption that you were aiming to do an abstract photograph. This is something I'm just assuming, since there was no reason to start saying that if you weren't aiming for it.
In sum, for me, for the reasons I've exposed, this is not really an abstract in nature, but it's close. And I do like the many things I can imagine here, as if this was not a small thing but a big one, a gelatinous mountain, or many, many more things (no time to say them all), or just an Yin-Yang shape of white and green. Be it what it may be for different people, there is something of abstract and something of macro photography in it and you've made me write more then even in the subject section of these critiques.
Regardless of what I can analyze aesthetically by recognition of forms/shapes and materials/elements, in my opinion, this is a very interesting but a little confusing photograph. Perhaps a little perplexing. And that can only be good for someone like me, but for other it might just be strange. And this is exactly because it is in a kind of a limbo between abstract and figurative expression. In one side you can recognize what is is and in the other it starts to change it's identity and turning into you own mind experience.
You have a great composition, that I've described above, and perspective works perfectly well here. There is no way for me to suggest anything better that this as the nature of this shot does not allow for any more understanding.
Use of camera,
If what I wrote about in the subject section corresponds to what you were trying to do, even if it is not exactly the same thing, you have used your camera very well. Everything has it's very well defined texture.
The motion blur on the bottom right could be more interesting... but I guess the shot is working well with it like that.
In this shot the foam is white and a bit grey and I think it could benefit from having a slight tint of colour. I like the way it's done but I guess it would be more appealing if it had a bit of colour, just a very little bit. The light is just fine, and I love the various reflections of it in the flat water surfaces, such as in the rough areas Perhaps it has some tiny bits of sparkle that are going a bit further from the whitest possible white in photography. Because a white with no texture is just an empty space, or a statement, and for it to exist and be accepted for what it is there needs to be a reason or an emotional justification. When going beyond frontiers we always need to find it's legitimacy, or else we're just going off for no reason.
But this is just for the foam... the rest is beautiful!