On cruises out of Australia does RCL present onboard accounts in US dollars and then convert it to Australian dollars or do they charge your credit card in US dollars? What is there exchange rate policy -e.g do they charge 4-5 cents below market rate?
To convert to the currency of your credit card RCL will use retail market rate on the day of the transaction (end of cruise) and then add a service charge of 3%. Check your credit card policy for foreign exchange charges and fees. They will usually be less than the 3%.
Least expensive way is to get a credit card in USD. You have to do the foreign exchange at some point and the best rate is usually done through online banking from your home currency to a USD account and then pay the USD cred