US dollars is the standard currency on most ships, although a few ships in
more exotic destinations use other currencies such as Euros. Travelers checks
can be cashed at the ship’s front reception desk with proper ID.
Some
ships accept cash for use in the casino, but otherwise remember that ships
operate on a “cashless society” basis with shipboard charges being posted to
your onboard account for settling at the end of the cruise with cash or a credit
card.
Some ships do offer currency exchange at prevailing rates if you wish to
carry local currency into your port of call, although US dollars, travelers
checks and major credit cards are accepted in shops and restaurants in most
ports of call.