CHARON ~ THE FERRYMAN OF HADES

In Greek Religion, Charon (Greek : Χάρων) is the ferryman of Hades. He receives the souls of the dead from God Hermes, who gathers them from the upper world and guides them to the shores of River Acheron. This river is the dividing line between the world of the living and the Underworld; and Charon provides passage with his boat.

Charon is the son of Erebus and Nyx. Some of his siblings incude Hypnos ( the God of Sleep ) and Thanatos (Death).Charon is depicted frequently in the art of ancient Greece. Attic funerary vases of the 5th and 4th centuries BCE are often decorated with scenes of the dead boarding Charon's boat.

 On the earlier such vases, he looks like a rough, unkempt Athenian seaman dressed in reddish-brown, holding his ferryman's pole in his right hand and using his left hand to receive the deceased.On later artistic depictions vases, Charon is given a more "kindly and refined" demeanor. Sometimes he is seen holding a double-headed hammer. Even though he looks elderly, Charon is extremely strong. Heracles wrestled with him when he descended into the Underworld and managed to subdue the Ferryman and make him  transport Him to the other side.

Paying a fee to the Ferryman

 A coin to pay Charon for passage, usually an obolus or danake, was placed in or on the mouth of a dead person. These coins had little value; yet, they were an indication that the deceased had been given proper burial and could make the trip. Those who could not pay the fee, or those whose bodies were left unburied, had to wander the shores of the Underworld for one hundred years as ghosts. If a soul tried to board the boat without paying, Charon used his pole to fight it away. The idea of roaming the shores of Acheron as a ghost was not desirable, of course- and Ancient Greeks buried their dead with the fee. This custom still exists in many parts of modern Greece.

Living people who want to visit Hades must also pay the ferryman.
Given the fact that they need two trips, Charon charges significantly more. Gods and Heroes such as Dionysos, Orpheus and Odysseus, travelled to the Underworld and returned, conveyed by the boat of Charon. 

Sources : Wikipedia , Ancient Greece Reloaded