The Sea of Monsters is a 2006 children's novel based on Greek mythology by the American author Rick Riordan. It is the second novel in the Percy Jackson & the Olympians series and the sequel to The Lightning Thief. This book chronicles the adventures of thirteen-year-old demigod Percy Jackson as he and his friends rescue his satyr friend Grover from the Cyclops Polyphemus and save Camp Half-Blood from a Titan's attack by bringing the Golden Fleece to cure Thalia's poisoned pine tree.
The Sea of Monsters was released on April 1, 2006, by Miramax Books, an imprint of Hyperion Books for Children, and thus Disney Publishing (succeeded by the Disney Hyperion imprint). It was generally well–received and was nominated for numerous awards, including the 2006 Book Sense Top Ten Summer Pick and the 2009 Mark Twain Award. It sold over 100,000 copies in paperback with over one million copies total and was released in audiobook format on September 6, 2006. The Sea of Monsters is followed by The Titan's Curse, the third book of the five books in the series.
Percy Jackson: Sea of Monsters, a film adaptation of the book, was released on August 7, 2013. The book was adapted for the second season of the Disney+ television series Percy Jackson and the Olympians; it premiered on December 10, 2025.
Plot After dreaming about Grover being hunted by a monster, Percy wakes on the last day of his peaceful seventh-grade year at Meriwether College Prep. He has befriended Tyson, a homeless child the school has taken on as a form of charity. In gym class, while playing dodgeball, Percy is attacked by Laestrygonians but is saved by Tyson and Annabeth, who was returning to Camp Half-Blood after having dreams about the camp in danger.
The three take a magical taxi driven by the Graeae to camp. There, they see campers led by Clarisse La Rue battling two Colchis bulls. Tyson is granted permission to move past the camp's boundary to save Percy again, revealing that he is a baby cyclops and Percy's half-brother, as he is also a son of Poseidon.
Someone has weakened the protective walls of Camp Half-Blood by poisoning the tree of the late demigod Thalia Grace (daughter of Zeus and childhood friend of Grover, Annabeth and Luke), leaving the campers vulnerable to future monster attacks. Camp activities director Chiron is accused of poisoning the tree and is fired. Before leaving, Chiron notes that only the Golden Fleece can save the camp.
Due to his charm and skill with a sword, Tantalus becomes the new activities director. As a reward for winning a chariot race, Tantalus sends Clarisse to find the Golden Fleece and forbids anyone else from leaving camp without his permission. After talking with the god Hermes about the fate of his son Luke, Percy leaves camp with Annabeth and Tyson to find Grover. Aided by a hippocampus named Rainbow, the trio reach the Princess Andromeda, a cruise ship filled with monsters and demigods that allied with the titan Kronos. On board the vessel, they are captured by Luke, who is working to revive Kronos. The trio escapes on an emergency lifeboat and takes shelter in a hideout that Annabeth, Thalia, and Luke built as children. A hydra attacks them there, but Clarisse saves them on her ship, the CSS Birmingham.
Annabeth, Percy, and Tyson join Clarisse's quest to the Bermuda Triangle. To enter the Triangle, the ship tries to pass between Charybdis and Scylla, who attack and destroy it. Clarisse gets separated from the others while Tyson seemingly dies in the explosion, so Percy and Annabeth board a lifeboat and head to the nearest island. After traveling through the narrow strait that Charybdis and Scylla guarded, the two land on the island of the witch-queen Circe. Realizing that she has turned dozens of men into guinea pigs, they turn the guinea pigs back into men and escape on the pirate's ship Queen Anne's Revenge, which Percy can control.
The duo manage to pass the sirens and reach the island of the cyclops Polyphemus, discovering that he has captured Clarisse. Before journeying to the island's center, Percy and Annabeth meet Grover, pretending to be a female cyclops to trick Polyphemus into not eating him. Tyson also arrives to help, having been rescued by Rainbow from the Birminghams wreckage. They find the Golden Fleece, but Polyphemus destroys the Queen Anne's Revenge, forcing the group to escape on Rainbow and a few other hippocampi. In Miami, Percy gives the fleece to Clarisse to fly back to camp alone as per her prophecy, but Luke captures him and the others. Taken aboard the Princess Andromeda, Percy makes contact with Camp Half-Blood through the goddess Iris and tricks Luke into confessing that he poisoned Thalia’s tree, exonerating Chiron, who is reinstated. Enraged, Luke battles Percy, but Chiron and other centaurs known as the Party Ponies arrive to rescue them.
The Golden Fleece is hung on Thalia's pine tree, which is cured. Having cleared the obstacle of Polyphemus luring in searchers through the Golden Fleece, Grover is given a furlough on his quest to find the god Pan. The camp holds a second chariot race, which Percy and Annabeth win with Tyson's help, who departs after accepting an offer from Poseidon to work in the god's underwater forges. However, the Fleece's magic is too strong, and it resurrects Thalia, providing another possible demigod for the Great Prophecy, which Percy realizes was Kronos' intention all along.
Characters
Percy Jackson The son of Poseidon; a 13-year-old demigod who goes to the island of Polyphemus in the Bermuda Triangle to find Grover and recover the Golden Fleece. He is accompanied by Annabeth and Tyson, his half-brother, on the quest. He is successful in the end and gives Clarisse the Fleece while he is attacked by Luke on his way to the Camp. However, he and his friends are rescued by Chiron and the Party Ponies. Annabeth Chase The daughter of Athena; a 13-year-old demigod who is a friend of Percy. She accompanies Percy to the island of Polyphemus and rescues him from Circe's island on the way. Annabeth is injured by Polyphemus and recovers with the help of the Golden Fleece. She accompanies Percy to Camp after Chiron succeeds in rescuing them from the hands of Luke and the Titan army. Grover Underwood The guard for Percy given by the gods, a satyr who has been captured by Polyphemus during his search for the wild god Pan. Due to his poor eyesight, Polyphemus mistakes Grover for a female Cyclops. He is rescued by his friends Percy and Annabeth. Clarisse La Rue Daughter of Ares who was given the quest of retrieving the Golden Fleece. With the help of Percy and his friends, she is successful in her quest. Percy gives her the Fleece that she takes to Camp Half-Blood. Polyphemus wishes to wed her after it is revealed to him that Grover is a male satyr. Luke Castellan The main antagonist, now 20; works for Kronos. He captures Percy and the rest before being thwarted by Chiron and his brethren, the Party Ponies. Tyson the Cyclops Percy's half brother; he is initially portrayed as a homeless child before Annabeth helps Percy realize that he is a Cyclops. After being claimed by Poseidon, Tyson experiences a great deal of prejudice against his race, although he befriends Charles Beckendorf who trains him in metalworking. He accompanies Percy and Annabeth in their quest and befriends a hippocampus whom he names Rainbow. He is very big and has one brown eye. When Clarisse's ship explodes, he is presumed dead until it is learned that he survived due to his immunity to fire and Rainbow rescuing him from the wreckage. Displaying a talent in metalworking, Tyson accepts an offer to work in Poseidon's underwater Cyclops forges and he crafts Percy a wristwatch shield as well as weapons for the second chariot race. Tantalus An ancient king and the demigod son of Zeus who was cursed for cooking his son and feeding him to the gods. As a punishment, Zeus killed Tantalus and took him to Hades in the Underworld who cursed him to always suffer starvation and thirst which takes the form of food and drink always moving away from him no matter what Tantalus does. After Chiron is fired under suspicion of poisoning Thalia's pine tree, Tantalus is hired as the new activities director at Camp Half-Blood where he is shown to be sadistic and cruel, greatly enjoying tormenting Percy and his friends and blatantly showing favoritism towards Clarisse La Rue. Tantalus reinstates the camp's chariot races and is more concerned with the outcome than the attack by Stymphalian birds. After Percy tricks Luke into confessing and exonerates Chiron, Dionysus dismisses Tantalus. In his last moments on Earth, Tantalus' curse appears to finally break as he catches a cheeseburger, but he is returned to the Underworld before he can eat it. Charles Beckendorf The friendly fifteen-year-old head of the Hephaestus cabin who goes only by his last name. Due to his father employing Cyclopes in his forges, Beckendorf lacks the prejudice towards Tyson that the other campers have and as a result, he befriends Tyson and trains him in metalworking. Beckendorf sets up the chariot race tracks and he faces off with Percy and Annabeth in the final race and is defeated thanks to Tyson's wristwatch shield invention. Rainbow A friendly hippocampus summoned by Percy for a ride to the Princess Andromeda who also befriends Tyson. He later rescues Tyson from the wreckage of the CSS Birmingham and helps to carry Percy and his friends to Miami. He transports Tyson to the underwater Cyclops forges of Poseidon at the end of the book. Agrius and Oreius The mythical bear twins who act as Luke's henchmen throughout the book. During Chiron's rescue mission, one of the Party Ponies kills Oreius with an arrow through the head as he prepares to rip apart Annabeth and Grover. Agrius is left so stunned that Blackjack the pegasus can break free, kick Agrius in the head, killing him, and escape. Circe A Greek goddess of magic and the daughter of Hecate and Helios who runs a spa on an island in the Sea of Monsters. Over the centuries, she is shown to have captured numerous ships and planes that have entered the Sea of Monsters, also known to mortals as the Bermuda Triangle, and transforms men into guinea pigs while giving women a spa treatment. Many of the men are then sold as classroom pets while she keeps the most troublesome in a cage. When Percy and Annabeth arrive on the island, Circe transforms Percy into a guinea pig, but Annabeth can break the spell by using special multivitamins provided by Hermes which also make Annabeth temporarily immune to her magic. Annabeth inadvertently turns back Circe's other caged victims, including Blackbeard and his crew who overrun the island while Percy and Annabeth escape on the Queen Anne's Revenge. Reyna Ramírez-Arellano The demigod daughter of Bellona who appears as one of the attendants on Circe's island who looks after Annabeth. Although she is unnamed in The Sea of Monsters, she is identified as one of Circe's attendants in the book The Son of Neptune and The Mark of Athena with Annabeth specifically recognizing her in the latter. Hylla Ramírez-Arellano The demigod daughter of Bellona who appears as an attendant on Circe's island, specifically the one who greets Percy and Annabeth upon their arrival on the island. While she is only addressed as Hylla in The Sea of Monsters, she reappears as the Queen of the Amazons in The Son of Neptune where Percy recognizes her from their previous meeting.