NEW YORK – The only thing more unlikely than a movie about a boy adrift on a ship with a Bengali tiger is the tale of the film’s star.

Teenager Suraj Sharma went along with his acting brother to a Delhi, India, audition of “Life of Pi” purely as a favor, motivated by the promise of a free meal.

“He said, ‘Come with me because I don’t want to go alone,’ ” Sharma recalled in an interview at Lincoln Center shortly before the film premiered at the New York Film Festival in September. “I said, ‘Fine, as long as you buy me a sandwich afterwards.’ That sandwich got me ‘Pi.’ ”

For a film about the wonder of faith, Sharma’s experience is one that stretches belief. Despite no prior acting experience or ambition, he managed to separate himself from 3,000 applicants and emerged through four rounds of auditions as the star in one of the most anticipated movies of the year.

For “Life of Pi” to work, Sharma – now 19, 17 when filming started – had to succeed. And many think the film, to be released Wednesday, not only works but is also a legitimate Oscar contender – a 3-D magic act from director Ang Lee that translates Yann Martel’s 2001 best seller into a colorful cinematic language.

In it, Sharma plays Pi Patel, who, as a child, precociously combines Christianity, Buddhism and Islam into his own blend of religion. When his family is uprooted to Canada, the ship taking Pi, his family and many zoo animals, sinks in a storm, leaving Pi alone and clinging to life in a raft boat.

Making the film meant working with one of the most revered directors in movies. It meant spending months shooting in India and Taiwan, where a giant water tank was built for scenes at sea. It meant learning not only how to act but also how to swim.

“I can’t put it in words,” says Sharma, a bright and earnest kid who humbly recognizes his good fortune. “It’s too much. It was emotionally and spiritually and physically exhausting. I would never be able to tell people what I went through exactly, but hopefully it will come through in some ways.”

It was a journey Sharma’s parents (both mathematicians, fittingly) had some reluctance about, as it would mean missing a year of school. Lee argued a year spent working on “Life of Pi” would be more rewarding than a year of school. Sharma’s mother performed a ceremony that made Lee her son’s guru – a new role for the director.

“I couldn’t even tell a joke in front of him. I had to behave,” Lee jokes. “I had to look after him. Normally when I work with actors, they move on and I move on. ... I can pretty much say he started at the top – getting this kind of reception and making a movie. So I want to make sure he’s grounded and still getting his education – not only in school but in life. He should be OK if he doesn’t get crushed by what’s coming.”

In “Life of Pi,” there’s nowhere for a young actor to hide, either. For a long stretch of the film, Pi is alone in the skiff with only the tiger, which was digitally added. Sharma had the added pressure of acting extensively in front of a blue screen, with little to go on other than Lee’s directions.

“Honestly, I still feel like I don’t know how to act,” says Sharma. “It was just him. I was just an instrument. He has this thing – suppose you’re really nervous and stressed out and going crazy – he’ll look you in the eye in a particular manner, and no matter who it is, you just go: whoosh! He’s like a Zen master or something. He makes you so calm that you just let him mold you into whatever he wants to mold you into.”

Sharma is now in his first year at Deli University where he’s concentrating his studies on philosophy.

“I’m pretty sure I want to end up in the film industry,” he says. “I don’t know if I want to act or not, but I do want to be part of making magic.”