Camera Work/Technical: Great focus, but there is a yellow hue beyond just the yellow of the submarine. It is more strong at the bottom of the frame.
Lighting: You did a nice job with exposure control here, but the shadow at the bottom left of the frame is a bit distracting.
Composition/Content: I think the cropping is just a bit too tight. You need just a little more space between the submarine and the left side of the frame.
My Opinion: Wonderful job meeting the challenge. Coming across a yellow submarine was a great find. With a few slight adjustments, this one surely would have pulled a much better score.
I was wondering how someone managed to find a submarine! I like how you used the foliage to frame it and the angle you choosed to shoot from. Seems to be a bit on the bright side.