From the moment I took on the project of directing Dolphin Tale, it was clear to me that the relationship between the boy, Sawyer, and Winter the dolphin was the movie’s emotional core. I wanted the audience to sympathize with and even envy Sawyer (What kid wouldn’t want to have a dolphin for a best friend?). But to have all these emotions ring true, Sawyer himself had to ring true. Too many films fall into the trap of having their child characters talk like adults or react to things the way an adult would. Because I introduced other elements of childhood wish fulfillment into the film—Sawyer’s friend Hazel lives on a fanciful houseboat with a crow’s nest/treehouse and a pet pelican who acts like a puppy, and she and Sawyer set up a crazily improbable carnival and fly a miniature helicopter—the film was in danger of feeling unreal and losing emotional resonance. Hazel and Sawyer had to be absolutely truthful characters, both in the writing and in the performing, to balance the film. Only by staying grounded in reality would the movie have the emotional impact I was looking for.

This meant casting was crucial. With the help of Kerry Barden and Paul Schnee, our casting directors, we auditioned hundreds of boys and girls.

One of the girls who auditioned, Cozi Zuehlsdorff, had never acted in a film or television show in her life. But I immediately recognized that she was bubbly, charming and talented, not to mention an extremely skilled actor for a girl who had only performed in local community theater. She was one in a million, and perfect for the role of Hazel. My producers at Alcon Entertainment, Andrew Kosove and Broderick Johnson, readily agreed.

But the role of Sawyer, our lead, was still cause for worry. We needed a young actor who was appealing, vulnerable (without being weak) and likable (even when silent and withdrawn), but without any of the falseness that you see in so many child actors.

I suspected I had found him when I met 12-year-old Nathan Gamble. A smart, skilled actor, Nathan is very grounded, experienced and talented. He has an actor’s relaxation, something that actors work all their lives to achieve. He is a great reactor who genuinely listens to other actors and can take direction beautifully. I only had three concerns. One: He wasn’t much of a swimmer! Two: He was very self-assured—could he really play the lonely, shy, insecure Sawyer? And three: Nathan had a big mop of blond hair that almost obscured his eyes. For the character of Sawyer, I knew his eyes would have to be the key to his performance, especially in the beginning of the film when Sawyer is so shy and silent.

At the screen test, I asked Nathan to brush his hair back so that I could see his eyes better. I finally took off my baseball cap and plopped it on his head, tucking his hair up under it, and had him read the scene again. I watched him carefully, and there it was: Every thought, every one of Sawyer’s insecurities, in that young actor’s eyes. We all agreed that we had found our Sawyer.

The first thing I did before we started shooting was to get Nathan’s hair cut and colored dark brown. It was amazing how it transformed him. I had our makeup crew do a little darkening of his lashes and eyebrows, and his eyes “popped,” as they say. They were amazingly readable and expressive.

Next, we worked on changing Sawyer’s posture. I told Nathan about Michael Chekhov’s “Psychological Gesture,” and with his shoulders hunched forward, he seemed to be hiding from the world. He understood what I was getting at and was able to do it beautifully. His movements, gestures and physicality changed. More and more I realized what a remarkable actor Nathan is, not just for a young actor, but for an actor of any age.

With his dark hair, expressive (and visible) eyes and command of the character, I knew we would have an outstanding lead performance. The only worry now was that the kid couldn’t swim very well, so we had him train with a swimming coach for the two weeks before filming began. And once again, young Mr. Gamble came through. His swimming improved so much that we never once used a double for it. Add to that his professionalism, dedication and all-around niceness, and I couldn’t have asked for a better leading man.

Contrary to public perception, directing a movie encompasses so much more than just dealing with what happens on the set and deciding where to put the camera. It is the vast amount of preparation, the thought put into the film and the building blocks of storytelling that matter the most.

My next task was to give Winter, the dolphin, as much onscreen personality as Nathan and Cozi. But that’s another story.