Rule of composition

I am not one for taking pictures. I wish I was, but I just don't have an eye for it. Which is why this picture surprised me. We were on a pier in San Diego and there were three pelicans hanging out and eating scraps that were thrown to them.

This is one of many pictures I took. When I reviewed it later I was surprised by how much I liked it. In fact I now have it tattooed on my back.

As I look at this picture with the rules of composition in mind I see that it may follow some of the rules, but it breaks some as well.

The rule of thirds
The pelican follows the rule of thirds by representing horizontally the left imaginary grid line of the photo. The boards on the rail also fall within a grid line. As focal points these elements follow the rules. The horizon line falls directly in the middle of the frame, which is contrary to the rules, however it is not a focal point of the photo, so I don't feel that it is an issue.

The diagonal rule
Overall this photo does not follow the diagonal rule. The lines of the trash can, rail, and horizon are all fairly straight.The pelican's beak is the only element of the picture that falls on the diagonal.

Vectors
The beak is in fact the most noticeable vector in this photo. The eye follows it like an arrow as it points down. When composing this photo for my tattoo I was very aware of the fact that the pelican is perched on a trash can with its beak directing one's eye to the can. The tattoo instead has a post with a splash of blue water around the bottom and the pelican's beak is not really pointing at anything.

I recognize that this photo doesn't follow the rules of composition completely, but despite that or because of it, I love the photo.