I love the first one. It is very crisp and clear. The nudibranch is in a very interesting position and you shot it from a good angle. If only that center branch of porites was not in the way it would be perfect. It is definitely one to be proud of.
The second. I love the subject and the composition. But the colour is not quite right. It has a green cast. Should be an easy tweak in photoshop. Also a one to be proud of.
The third, I think has more sentimental value to you than anything else. I bet this fish was one of the highlights of your trip and thus the picture of it brings back fond memories.
The picture is not nearly as good as the first two. It is in-focus but has little else going for it. The DOF is too great and the very busy back/foreground cause the fish to get lost in the scenery. The strait-on com composition does not do the fish justice. A front 3-quarters shot would be much better.
Both of your first two I would say are definately POW material, the third is not nearly as interesting.