Jack Sparrow: Poseidon's Peak

Pirates of the Caribbean: Jack Sparrow: Poseidon's Peak is the eleventh book in the series of young reader books. It was published on April 29, 2008 by Disney Press, and written by Rob Kidd.

Publisher's Summary
Having been recently betrayed by his last crew member, Jack finds himself all alone on perhaps the most dangerous quest of his young life. Jack is on a mission to find something he isn't even sure exists - the mythical Trident of Neptune. But there's a band of pirates who are also looking for the treasure. Will they, or Jack, find it first?

Summary
After acquiring a new boat, Jack sets off to find the fabled Poseidon's Peak and the treasure it holds. He arrives on a deserted island and runs into an sailer who is badly hurt and has amnesia. Following a night of fitful dreams the sailor remembers that his name is Bill and the two of them trek inland to find any clues to where Poseidon's Peak might be. Before long the two are captured by the natives, with Bill inexplicably able to translate what they're saying and are challenge to fight for their lives. Jack cheats and the both of them run into someone very familiar, Constance Magliore, who the natives worship since she swam out of the sea. After getting away from the natives, Jack has the idea of lashing logs together to make a raft to escape the island and while they search, they unearth a chariot covered in sea life. They get on the chariot and it prompt takes them out to sea where the jump off it before it submerges and end up on a small rock in the middle of the ocean. Jack, in a fit of anger, tosses Constance off the rock which causes her to lead them to an underwater cavern. Constance proceeds to lead them through tunnels that seem to go in circles until Jack meets a group of people that are very familiar to him, the former crew of the Barnacle (sans Fitzwillim), along with Arabella's mother and her crew. Jack is especially glad to see Arabella but is dismayed when she runs up and kisses Bill who has regained the rest of his memories and says that he was rescued by Captain Smith's ship sometime after they had split from Jack. Not to long after this, a group of mermaids, of a higher level than the ones Jack has met before, ask them to keep the items belonging to Poseidon (his trident and chariot) away from Davy Jones who would use them to manipulate their kind. Shortly after the request, an unwanted face shows up riding the chariot and wielding Poseidon's trident, Captain Torrents.