I am not sure how helpful this critique will be given that so much of your piece succeeds on every single level but here goes.
The central figure, a great modern take on classic portraiture/mythology, absolutely commands my attention every single minute. The piece is successful at directing my perception from several different points (the trident, the face, the left hand, and the cloth at the chest) and my eyes are constantly moving around the piece. The artist rewards my efforts with stunning details in cloth, skin, and lighting effects.
As a result the background is minimally necessary and the artist executes it exactly as it should be; but perhaps even more than is accomplished. It may possibly be due to the pastels as a medium or the scale of the image (since it is significantly shrunk down for digital viewing) but I found the clouds in the upper corner to pull me out of the picture.
By that I mean the central figure, his trident, and all the details within are startlingly real but the clouds lose a large amount of that punch and appear as a picture within this picture (such as part of a backdrop for a photograph). It is not a question of technique (it is really difficult to even bring that up) so much as how much you notice the sky.
The ocean by contrast is very diluted into the grays, browns, and blues of the wispy haze but still accomplishes its function perfectly. You always know it is the ocean with no questions asked; I think that it would work better if the sky was less opaque so the complementary oranges and yellows do not draw me away from the figure as much.
However this is just such a minor complaint on a piece already near the ideal. Composition is fantastic and engaging (I really love close-range pieces) and the technique is just mind-blowing (I sometimes cannot tell if the face is not just a photograph.)
I can't give this image full marks for originality since I see so many artists here; new, old, and all at once (subject matter-wise at least). But this piece is mesmerizing, modern, and different enough to really hold me in place.
Honestly I could look at this picture for hours and I really wish that I could see it in person. I sincerely hope this goes into a gallery/museum exhibit as soon as possible; I am truly excited to see where else you go from this point. "Wow" is all that I can say really.