The Princess Andromeda was a cruise ship captained by Luke Castellan and the primary living space for Kronos' Army. It was destroyed by Percy and Beckendorf, resulting to the death of the latter. It contained Kronos' sarcophagus, and could travel faster then any mortal ship, possibly assisted by magic or a titan. The Princess Andromeda contained all sorts of monsters, including Dracaenae and Drakons.
Luke is in control of the ship. Hermes sends Percy onto it so he can talk to Luke, which Hermes leaves Percy to do himself. The ship has many mortals on it, but they are all under some sort of trance that prevents them from seeing the monsters inhabiting the ship. After Percy, Annabeth, Grover, Tyson, and Clarisse take the Golden Fleece from Polyphemus' island in the Sea of Monsters and return to Miami, Luke confronts Percy to take the fleece from him. However, Percy tells him that he doesn't have the Golden Fleece anymore nor does Annabeth, Grover, or his cyclops half-brother, Tyson. He informs him that they had let Clarisse fly home with it ahead of them. The Party Ponies attack at the right moment once Luke made a mistake and said, "Kronos was right. You should have been killed, Percy." Putting Kronos' army in confusion when Luke and Percy are dueling to the death. Along with the Party Ponies was Chiron who saved Percy, Annabeth, Grover, and Tyson from another fight with Luke and his army aboard the Princess Andromeda.
Percy and Beckendorf board the ship, with the intention of destroying it with Greek fire. They notice that it is filled with Telekhines and other members of the Titan Army, and that the once plush carpets had been ruined by slime. There are no more mortals on the ship which Percy thinks didn't get to leave with their bingo winnings. Their time is cut short when two Telekhines enter the engine room while they are planting the explosives. Percy buys Beckendorf some more time by running through the heavily armed crowds of monsters and is caught by Luke/Kronos. Then Beckendorf is forced on the deck as two monsters claim they captured him heading for the engine room to plant explosives. Percy (and Luke shortly after) figure out that Beckendorf pretended to head back to the engine room so they wouldn't send anyone to check. Beckendorf activates the trigger to the explosives and Percy escapes by jumping into the sea, but Beckendorf isn't so lucky. While the plan to destroy the Princess Andromeda was a success, Percy thinks that it was too easy, which is true as Luke was only using it to give the demigods a false sense of security.
The boat is named after Andromeda. She was a girl whose mother bragged about being more beautiful than Aphrodite and nereids. Because of her foolishness, she angered Aphrodite and the nerieds, who complained to Poseidon. He sent a sea monster to her city for revenge. Her mother chained Andromeda to a rock, exposing her to their monster, hoping her daughter would make a good sacrifice to the gods. However, Perseus, the first and the son of Zeus, found her and freed her. Then, during the wedding, Andromeda's former suitor shows up with an army of 200 men. Perseus kills the attackers with Medusa's Head, taking it from it's cloth and showing it to all those that looked at it, turning the army to stone instantly. In Greece, Perseus married Andromeda and had several sons and one daughter, one of their sons, named Perses, stayed behind to rule his grandfather's kingdom when he died, and became the later father of the Persians.