Carnival Cruise Lines “appreciates” the United States Coast Guard for escorting the disabled Triumph to safe docking at Mobile, Ala.

But pay the taxpayers back for responding to the five-day ordeal?

Apparently not.

Sen. Jay Rockefeller, D-W.V., is not happy. As chairman of the Senate Commerce, Science and Transportation Committee, he wants to know how much it cost taxpayers to help the crippled ship and whether the Coast Guard, which is still calculating those expenses is going to seek reimbursement.

But asked about paying back the Coast Guard, Carnival spokesman Vance Gulliksen said that “traditionally, this is one of the many services the USCG provides, and we greatly appreciate their assistance.”

Keep in mind that while the bulk of Carnival’s business is in the U.S. (including cruises that depart regularly from Charleston), the corporation pays relatively little in American taxes. Specifically, it paid a 1.1 percent rate on $11.3 billion in profits over the last five years. Carnival’s sweet deal is courtesy of a U.S. tax loophole that allows companies incorporated overseas to avoid most taxes — even when they do most of their business here.

Carnival has promised all of the 3,000 Triumph passengers a refund for their trip and transportation expenses, $500 and a future cruise credit equal to what they paid to be on the ship.

Carnival’s maritime mistake was an expensive one. But unless the Coast Guard is able to extract reimbursement from the corporation, Carnival’s rescue was a steal.