Check your credit cards. If you have one that does not charge an exchange fee use it. Check with your bank about making foreign transactions too. You will want to let them know you will be traveling in Greece or they may put a block on your account and give you a call at home to let you know their have been suspicious charges.
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014, 2016
Star Clippers: Royal Clipper 2015