River tugs will perform Fleur De Lis – spraying water from their fire cannons.
Vessels currently within Liverpool and Wirral dock systems, including at Cammell Laird in Birkenhead, also sounded their whistles in unison, showing solidarity with the maritime salute.
Lord Mayor of Liverpool, Councillor Roy Gladden, said: “With Liverpool’s world-renowned maritime heritage it feels right that we use the River Mersey to pay a special tribute to Queen Elizabeth II.
“Following discussions with our maritime community, there is a real appetite for the working vessels to pay their own unique mark of respect to the monarch.
“This tribute will be a rousing chorus of whistles and horns to echo along the shore of the Mersey, a river upon which many of Her Majesty’s vessels have visited.”
Mayor of the Liverpool City Region, Steve Rotheram, said: “This is going to be a really special moment for the public to come together on the banks of the River Mersey to observe a unique tribute to the incredible life of Her Majesty Queen Elizabeth II with a magnificent maritime spectacle.
“Our region’s maritime links to the Royal Family run deep, with both Her Majesty and royal vessels having visited the Port of Liverpool several times throughout her 70-year reign. This is a chance for members of the seafaring community, local residents, and visitors, to pay their respects on our iconic waterfront in the way that only our region can do best.”