Princess Cruise Lines will pay a $40 million fine and for deliberately dumping waste into the seas it sails in and attempting to cover it up, authorities announced Thursday.

The fine imposed on the California company for polluting US waters with oil waste from the Caribbean Princess is the largest ever criminal penalty for deliberate vessel pollution, the US Justice Department said.

"The pollution in this case was the result of more than just bad actors on one ship," the department's chief environmental prosecutor John Cruden said in a statement. "It reflects very poorly on Princess’s culture and management. This is a company that knew better and should have done better."

Prosecutors said the pollution was discovered after a recently-hired marine engineer on the Caribbean Princess revealed the existence of a "magic pipe" used in August 2013 to spew 4,227 gallons (16,000 liters) of oily waste off the coast of England.

The US investigation began after British coast guard officials tipped off their American counterparts. The Caribbean Princess began making illegal discharges in 2005, a year after the ship entered service.

The ship's chief engineer and senior first engineer ordered a coverup, including simultaneously discharging clean seawater so that digital records would indicate that a legitimate discharge had occurred, according the Justice Department.

Investigators uncovered other illegal practices intended to hide oily discharges by the Caribbean Princess and four other Princess vessels, meaning that illegal discharges in US waters were likely.

Princess is a subsidiary of the cruise lines giant Carnival Corporation, the world's largest cruise company. 

As part of the plea agreement, Princess agreed to plead guilty to illegal dumping, and the eight Carnival cruise companies will be subject to a court-supervised environmental compliance program for five years, the Justice Department said.