When he arrives, a nereid gives Percy three pearls saying they are gifts from his father, Poseidon. Percy takes the pearls with him to the Underworld. Hades
tries to kill Percy, Annabeth, and Grover when they smash the pearls at
their feet, the pearls then carry them to the middle of Santa Monica
Bay because, as the Nereid said, "What belongs to the sea returns to the
sea."
