Charon, in Greek myth, rowed across the rivers of Styx and Acheron in a boat. This was what Charon used to take the souls of the dead across the rivers, and it was the only legitimate way to cross the rivers of the Underworld.
In God of War: Chains of Olympus
During the events of God of War: Chains of Olympus, Kratos crashes the chariot into the outskirts of the Underworld. When he arrives at the Docks of Charon, Kratos rings the bell to summon Charon. Charon's Ferry is an extremely large boat. At least 50 feet long, it has no visible sails, but it is moved by large oars which protrude from the side of the ship. One special feature of this boat is that Charon can use the ship to send a wave of green flames from a structure which had the appearance of a fireplace with three columns. The flames could kill anyone blocking their way. This structure also seemed to control Charon's life. After Charon refused to give Kratos passage across the river, he and Charon fought on the deck of the Ferry. Charon subdues Kratos, and sends him to the Jails of Tartarus. Kratos fights his way through and comes back to the Docks. After Kratos fought and defeated Charon, he gained control of the Ferry, and used it to reach the Temple of Persephone.