These sort of shots must be so difficult but as I have nothing or the knowledge to compare it against together with the challenge meeting I will give you a 7
This is beautiful! Fantastic blue shades, sharp contours and water surface do the job. It"s gracious too. Well exposed for an underwater shot. Nice diagonal, that could have been enhanced by a square framing (cropping left). Just regret that the dolphin is seen going away and not coming in your direction.