In a history-making development, P&O Cruises will welcome its first-ever newbuild. The still unnamed ship will be able to accommodate 4,200 passengers, making it the biggest in the fleet.

Set to debut after P&O's next largest ship, the 2,250 passenger Pacific Explorer (currently sailing for Princess Cruises as Dawn Princess), it will also become the newest ship ever based in Australia and the youngest for P&O, whose other ships are more than 20 years old.

Scheduled for delivery between 2019 and 2020, the new ship is one of four to be launched by parent company Carnival Corp. & plc, as part of an agreement with Italian shipbuilder Fincantieri S.p.A.

Princess Cruises will also receive a 3,560-passenger ship, to be based in an undisclosed location, and two more will be built for Costa Asia.

"We will deliver on our fleet enhancement plan with the construction of these four new, exciting ships that are consistent with our long-term strategy of measured capacity growth over time," Arnold Donald, CEO of Carnival Corporation, said in a press release.

"These strategic investments in new ships that wow our guests are an important part of our measured growth strategy, which includes replacing less-efficient ships with newer, larger and more efficient vessels over a very specific period of time."