What first drew me to dwell on your photograph were the colours and the way the water looks from below the surface. Secondly, the turtle's gaze is upon you and inspires me to wonder what it's thinking as you take it's picture.
This is an incredible shot of an amazing animal for the simple fact that it is underwater. Not all of us have the means nor the ability to get in the water the way you do to capture just the right moment with the creatures you've encountered.
This is a photograph that I'd not mind having on the wall by my computer or another room in my home.
I'm not sure how to judge technique as I'm not a photographer but it seems to be very well done. Originality I didn't rate as high only because there are other photographs like this taken by others. The impact is high because it drew me in from the very beginning. Vision is the same.