The "coming of age" novel is called a "Bildungsroman." This is when the main character matures, has moments of self-discovery and this can involve a mental and/or physical journey.
In Life of Pi, you have a situation where the main character finds himself in a situation where he must “come of age” in order to survive. “Coming of age” frequently means a progression from childhood to adulthood and usually takes place during adolescence. It can refer to sexual maturity, the age of self-awareness and responsibility or it is marked by some ritual or life event. In Pi’s case, his defining moments are the events he endures subsequent to the ship sinking. His “coming of age” moment is not just a typical progression of child to adult. If the ship had made it to Canada, he would have had a difficult time at first, being an immigrant, but he would have been faced with the typical rigors of being a teenager, dealing with his peers and learning about himself and the world.
But Pi was forced to come of age in order to survive; not just “fit in.” So, his defining moment is quite different than the typical sexual, legal or responsible maturity. If you want to pursue this thesis, the basic premise is that Pi’s development was based on survival and finding meaning during that difficult time. I’ve often heard that kids who have tough childhoods or trouble fitting in “survive” high school. This is hyperbolic because their lives were not in danger. It’s just that certain pressures can seem overwhelming and this is a period of physical and mental change in a person’s life, so this period is just downright dramatic. Pi’s case is just atypical. His defining moment has nothing to do with social pressure or pressure from his parents to be a certain way as a young adult. In fact, any and all pressure during his time at sea comes from himself. He must rely on what he’s learned (from his parents and teachers) in order to survive. Ultimately, he must rely on himself and he must in fact pressure himself, keep himself on his toes in order to survive. His “coming of age” has nothing to do with conformity or dealing with social and cultural rules. It has everything to do with self-preservation and finding meaning in the act of survival.
I suppose, in a sense, he has to get along with Richard Parker, to stay alive. But this is not the same as “fitting in.” Whereas most kids learn their niche or reach some level of maturity that is recognized by society and their peers, Pi learned how to survive on his own. This defining moment doesn’t really have the socially recognized status that one gets when one loses their virginity, gets a driver’s license, votes, gets married or buys a house, but I would argue that defining moments like Pi’s trumps all of these.