The Princess Royal reviewed the seven ships in P&O Cruises' fleet at Southampton to mark the company's 175th anniversary.
Thousands of people lined the waterfront as the ships took the royal salute before departing on cruises.
This is the first time the ships - Adonia, Arcadia, Aurora, Azura, Oceana, Oriana and Ventura - have gathered together in their home port.
On Azura, ballerina Darcey Bussell, who named the ship in 2010, was presented with seven captains' hats.
However, rain did threaten to spoil the party as a performance by the Red Arrows had to be cancelled, and traffic backed up around the city.
Meanwhile, some passengers complained of "organised chaos" as they waited hours for transport to get home.
A total of 15,000 passengers disembarked and 15,000 new passengers boarded the ships during the day, with the whole event bringing an estimated £17 million toSouthampton's economy.