Reciprocal Operating Permits can get a bit confusing depending on what country you wish to operate. I suggest consulting the ARRL web page ( as I have found it to be a good place to understand this subject as not all countries participate in CEPT or IARP. In my case, the ship we were on was flagged in Bermuda. So for all intent and purpose, when you are on board the ship and at sea, we were in Bermuda. I had no  intent of operating while we were sailing around the Mediterranean. I wanted to enjoy each stop as well as not have to manage what countries territorial waters we were in and if they were a part of CEPT and what call sign prefix or suffix I needed to use... 
I used the information found at this web site to understand what I needed to do to obtain a Reciprocal Operating Permit in Bermuda ( It is quite an easy process. Beverly Evans is the contact and it is a great thing that Bermuda does not charge any fee to obtain the permit. To get the permit I emailed Ms. Evans with the following information:
  1. What I wanted to do:
    • Operate from a Bermudian flagged ship as an Amateur Radio Operator
    • Requested a reciprocal Operating Permit.
    • Dates we would be traveling
  2. A copy of my Amateur Radio License
  3. Name of the ship and location where we would embark
Just a few days later Ms. Evans sent me an email with my Reciprocal Operating Permit attached in pdf form... With permission from Princess Cruise Lines, the ship's Captain and a Reciprocal Operating Permit from the country of the ship's registry (Bermuda) we had all the paperwork we needed to operate with all necessary permission while aboard ship...