Slow down
Your work is not bad, per se, but it really does require you to take more time, in order to get the fundamentals right - smaller fore fins and a set of fins under the belly, about mid way between the dorsal and tail fin.
The other main issue is that the gills are too far back - they generally occur on the Great White in front of the fore fins and extend down further.
A little rushing costs you for this piece - a few little errors take so much away from the piece - it's all in the detail, so use a search engine and get good research material before you start.
[Review Request Club]