It's an island made entirely of seaweed, full of meerkats and freshwater ponds. It gets even stranger when dead fish rise to the surface of the ponds at night and disappear by morning. At first Pi thinks the island is a delusion, “I was getting used to my delusion. To make it last I refrained from putting a strain on it; when the lifeboat nudged the island, I did not move, only continued to dream.” But Martel spends too long with the island for it to just be a delusion. Pi describes the island very precisely. It just doesn't have the hazy feel of a delusion. One possibility is that the island represents some type of faith. When Pi first steps onto it he says, “My foot sank into the clear water and met the rubbery resistance of something flexible but solid. I put more weight down. The illusion would not give. I put the full weight of my foot. Still I did not sink. Still I did not believe.” Like Saint Peter trying to walk on water after he sees Jesus do it?
But maybe the island doesn't represent the type of faith Martel thinks we should have. Because, the algae turns out to be man-eating algae. It's an island that can consume you if you're not careful. Meaning, if you settle yourself with physical comfort (all the food and water) it turns into a type of spiritual death. If your faith is too easy and you no long, brave, and stormy seas, then you're no longer experiencing real faith. Notice too that Pi really tames Richard Parker on the island. Richard Parker, like the ocean, is part of Pi's spiritual trial. What do you do when your spiritual test (Richard Parker) follows your every command? You leave. “By the time morning came, my grim decision was taken. I preferred to set off and perish in search of my own kind than to live a lonely half-life of physical comfort and spiritual death on this murderous island.” Like all of Martel's symbols and allegories in Life of Pi, the island ends up being more mysterious than one might think.