These are indeed great shots of a fantastic duck. (I agree the duck seems to know it's a handsome one itself!)
You have done a good job working together with a good lens - fora very satisfactory (understatement!) outcome!
The water looks maybe a bit too "silky / mercury-like" if you know what I mean.... (that's just my subjective opinion, and I'm not sure if that's what Jules meant in her post and what you were referring to as well when you replied to that...)
But otherwise these two photos are great. I wish you all the best with your school competition. I think these two photos compliment each other as one the duck is on the rocks (no pun intended) and the other it is in the water. Let us know how you go.