Love how the hippo is peeking up at you. I think what may hurt you on this shot is the number of conflicting patterns (rock, hippo hide, water) that all pull in different directions. I also think there is too much contrast between the rock and the hippo, but not enough on the hippo himself (would like to see more detail in his hide). Still an interesting shot and right place at right time.
Odd critters aren't they?
This could have really been much more effective had the eye and area around it not been so deep in the shadows. Not a difficult fix in Photoshop using levels in a new layer via copy, then soft brush erasing back the areas that didn't need to be brightened up.
Jst a thought.