Japanese officials have taken control of the country's biggest car ferry and transformed its 630 cabins into cells.
The ship is called the Sunflower Tomakomai, but has been nicknamed HMS Hooligan.
Football thugs being taken to a detention centre near Tokyo could be locked up in the ship's cells or possibly the hold.
The Japanese are particularly worried about England's match against Argentina.
They fear the evening kick-off and the fierce rivalry between the fans could lead to all-day drinking and violence.
An extra 7,000 police are expected to be on duty for the match on Friday 7 June.