There are many religious items throughout Pi's house; so many, in fact, that the author describes Pi's home as a temple:
Upstairs in his office there is a brass Ganesha sitting cross-legged next to the computer, a wooden Christ on the Cross from Brazil on a wall, and a green prayer rug in a corner.
In addition to these items, Pi also has a likeness of the Virgin Mary of Guadalupe, a green prayer rug in the corner of his bedroom, and a Bible next to his bed. Obviously Pi is influenced and inspired by several different religions: Hinduism, Islam, and Christianity.
Pi's family practiced Hinduism before his birth, so he was basically born into that religion. But Pi also finds himself drawn to the story of Christ after an interaction with a friendly priest named Father Martin. After this encounter, Pi considers himself both Hindu and Christian. Finally, when Pi is a teenager, he meets a Muslim holy man named Mr. Kumar who explains the tenants of Islam to Pi; Pi becomes so fascinated with Islam that he regularly visits the nearest mosque and prays with Mr. Kumar.
Since all three world views are so important to Pi, it makes sense that he would want physical manifestations of all three present in his everyday life. His faith in all three religions clearly helped him survive his ordeal in the lifeboat.