Rent A Powerboat I Am Planning To Travel To Greece This Summer And I Want To Rent A Boat. Is There A Need For A Licence?

I am planning to travel to Greece this summer and I want to rent a boat. Is there a need for a licence? - rent a powerboat

I plan to use a motorboat cousins in Greece and, if possible, a rental to one of the islands do. Is there a certificate for international aviation, as they have for cars?