Keep in mind if you use a debit card, that some times the businesses will place a hold on your account before that actual purchase is run through which could leave you short of accessible cash. Especially if you use your debit card for your on board account. The cruiselines will place a hold on a certain amount of money but not actually charge the card until the end of the cruise. Example, they might place a hold for $500.00 on your card, then at the end of the cruise run the actual amount you charged, but not release the hold until 2-3 days after the cruise.
I had clients this happened to, after leaving the ship they got ready to put gas in vehicle and did not have access to their money between the charge and the hold, spent hours on the phone with the cruiseline trying to get it released, they couldnt get home without the extra funds.