Being dead is normally a pre-requisite! You also need a coin to pay Charon, the boatman to punt you across. This is the origin of putting coins on the eyes of the dead (it also keeps them shut) and for sailors wearing rings in their ears - originally, it was a hoop made from a gold coin to ensure they had the fare with them.
The River Styx actually exists!! i've been there!! It's about 200ft underground at Baia, in Italy. Read the book "In the footsteps of Orpheus" by FR Paget, to find the exact location.