Treasure-hunter Ramos invites Fujita on a hunt for treasure along the Amazon river, and they are accompanied by Professor Yoshioka. They eventually find a complete Mayan city underground, but are captured by the villagers who plan to sacrifice Sara to their gods. However Fujita uses a dinosaur-like carving to activate a secret switch which releases the huge Pororoca tidal wave, into the cavern. While they are being swept underwater, they see what appears to be a huge pliosaur.