This chapter is entirely dialogue. It also contains Pi's second version of events at sea, and thus significantly complicates everything you've read up until this point. Here we go.
Mr. Okamoto tells Pi that they don't believe his story.
He tells Pi that for starters bananas don't float. (Remember Orange Juice and the island of bananas?) Pi gets Mr. Okamoto to put a banana in the sink and test his objection. The banana floats.
Mr. Okamoto says there are plenty of other problems with Pi's story like fish-eating algae and tree-dwelling rodents. Mr. Chiba is of no help. Mr. Okamoto also points out that no one has found a tiger yet in the nearby jungle. And that he's not so sure, anyways, about the RP part of Pi's story either.
Pi responds with a couple stories and an assertion that every city is probably full of wild animals people don't notice. He also maintains that just because his story is "hard to believe" that doesn't make it invalid or untrue. Again, Mr. Chiba is of no help.
Mr. Okamoto points out two unlikely elements in Pi's story: the Frenchman and the meerkats. Pi defends the existence of each of these elements but not their likelihood.
Mr. Okamoto is losing his patience and asks for "the straight facts" (3.99.211). Pi counters that language always an invents and that basically there is no such thing as "the straight facts."
Pi and Mr. Okamoto agree that Mr. Okamoto wants a story without the animals.
Pi says okay and tells a version of his story without animals. It's horrific and brutal. Pi condenses the story we've already heard and substitutes his mother for Orange Juice, a cook for the hyena, a Taiwanese sailor for the zebra, and himself for RP. (See "Symbols, Imagery, Allegory" for more.)
Mr. Okamoto and Mr. Chiba talk in Japanese. They figure out the substitution scheme listed above.
Mr. Okamoto asks Pi tons of questions about the actual sinking of the Tsimtsum. Pi really doesn't have any answers and Mr. Okamoto's line of questioning seems specialized and narrow. And also ignores the pathos of Pi's ordeal.
Pi corners Mr. Okamoto and Mr. Chiba in the conversation. Neither version really tells them anything about the sinking of the ship. And so neither story makes much of a factual difference to their investigation. So which story do they prefer? They prefer the story with animals. Pi responds: "And so it goes with God" (3.99.433).
The investigators and Pi say goodbye to each other.