Carnival says all maritime interests must assist without question those in trouble at sea, a duty that would not include reimbursing the U.S. government nearly $780,000 for costs associated with the rescue of the disabled Triumph cruise ship.

Carnival released letters Friday replying to an inquiry by Sen. John D. Rockefeller IV (D-W.Va.), who chairs the Senate Commerce Committee, about the Triumph stranding and the cruise line’s overall safety record. Among Rockefeller’s questions was whether Carnival would repay the government for Coast Guard costs in the Triumph case as well as $3.4 million to the Coast Guard and Navy from the 2010 stranding of the Carnival Splendor in the Pacific Ocean.

“These costs must ultimately be borne by federal taxpayers,” Rockefeller said in his March letter, adding that Carnival appears to pay little or no federal income taxes.

In response, Carnival said its policy is to “honor maritime tradition that holds that the duty to render assistance at sea to those in need is a universal obligation of the entire maritime community.” The cruise line noted that its ships participate in rescues at the Coast Guard’s request, including 11 times in the past year in Florida and Caribbean waters. It did not make direct reference to repaying any money.

In a statement, Rockefeller called the response “shameful.”

Rockefeller’s letter asked Carnival whether the money it pays in taxes covers the costs of various federal benefits it receives, a question the cruise line did not directly answer. It mentioned port taxes and fees and other payments and said it paid $16.5 billion in wages to U.S. workers in 2011.

The exchange marked the latest chapter in the saga of the Triumph, which was disabled by an engine fire during a cruise in February in the Gulf of Mexico. Thousands of passengers and crew had to endure five days at sea with no power and under squalid conditions while the 900-foot vessel was towed to Mobile, Ala., where it continues to undergo repairs.