A commersons dolphin swimming through the ocean.

Started as some practice for dolphins, since it has been a while. Originally the dolphin had a more cartoonish look, but that changed as it didn't look right (I already nicknamed the dolphin Mr. Grumpy...)
I'm quite happy with the result, but I can't get the lighting/shading right. I spent nights working on it, but I can't seem to get it fixed.

Any comments or advice are more than welcome!