Quite simply, Pi also loses his way of life. Before the sinking of the Tsimtsum, Pi is struggling with typical coming-of-age ideas, especially religion. He is misunderstood by his family, but is handling life just fine. When his father decides to move the family business (the zoo) out of the area, this is when Pi's life changes. The Tsimtsum sinks, and Pi is forced to move from a life where he struggles with "normal" problems to the problem of survival.
Piscine Molitor Patel (who creates the nickname of "Pi" in order to prevent being called "pissing" and in order to exhibit his smarts) switches from the normal life of a young man into a teen fighting for survival on the ocean when the Tsimtsum sinks. Most of this survival (after the other animals are killed in different ways) involves his dealings with Richard Parker, the over four hundred pound Bengal tiger that is also adrift on the small dingy. Why does Pi befriend the tiger? Mostly to combat fear:
I must say a word about fear. It is life's only true opponent. Only fear can defeat life. It is a clever, treacherous adversary, how well I know. It has no decency, respects no law or convention, shows no mercy.
One of the ways Pi defeats fear is by vowing to keep Richard Parker alive. The two create a bond between a thinking, living being and an animal that runs on instinct. It is when his small dingy lands that Pi loses something else: Richard Parker. And Pi loses him FOREVER. It is a heartbreaking scene, but one where Pi learns a lot:
Dare I say I miss him? I do. I miss him. I still see him in my dreams. They are nightmares mostly, but nightmares tinged with love. I still cannot understand how he could abandon me so unceremoniously, without any sort of goodbye, without looking back even once. That pain is like an axe that chops at my heart.
In conclusion, it's important to note that this is a coming-of-age story, or a bildungsroman, because Pi grows up in the process.