The work by Founded depicts Brydon as a "newly converted cruiser" stepping off the ship to enjoy onshore activities in Mediterranean locations, taking various selfies.
The campaign aims to attract new customers to cruises, debunking any negative preconceptions such as having to spend too much time on board.
It launches during the Downton Abbey Christmas special on ITV.
The film was created by Paul Hodgkinson and Ross Garden, and directed by Declan Lowney through Another Film Company. Media planning and buying was handled by the7stars.
Christopher Edgington, the marketing director at P&O Cruises, said: "Founded’s latest work underlines the sheer breadth of experiences that can be enjoyed both on and off shore, and showcases all that a P&O Cruises holiday has to offer.
"We’re delighted with the success of the campaign so far, and confident it will inspire many more holidaymakers to try cruising."