I wondered about this issue of PCCs, too. "These documents are to be provided for each country other than Canada, in which you have lived for
six consecutive months or longer since reaching the age of 18."
You said that your husband's ship was US based (Princess Cruises Ltd?), but that flies the flag of the Bahamas. There are interesting Maritime Laws, and flying a "flag of convenience" saves companies a lot of money. One of the issues is that a foreign ship cannot sail an entire cruise between US ports. It must sail into at least the port of ONE foreign country. This is why the Alaska cruises stop in Vancouver or Victoria, the Hawaiian cruises stop briefly in Ensenada, Mex before returning to LA, etc. THIS is what makes me think that a PCC from the US would not be required, as your husband's time "in??" the US would not be considered CONTINUOUS. The only glitch I can think of is that his passport would not be stamped each time he entered/departed that foreign country. It will be interesting to see what others have found out about this.
http://www.commercialdiplomacy.org/ma_projects/magee3.htm E.2 Foreign Competitive Advantage in Operating Ships
There are several competitive advantages to being a foreign flagged cruise ship, they are:
No citizenship requirements for ownership, or crew
No corporate income tax, as required for U.S. flagged operators
Ship construction costs approximately ½ to 2/3 the cost of U.S. built ships.
Crew costs approximately ½ the costs of a U.S. crew.
The main disadvantage is that in order to operate in U.S. waters,
all foreign flagged ships must make a trip to a foreign port, which makes planning itineraries tricky.