Authorities were called to the dock at 3.54pm today following reports that the Yellow Duckmarine amphibious tour bus had sunk.
Police and ambulance arrived at the scene to help with the rescue operation, as a large crowd of people gathered nearby.
North West Ambulance Service said that everyone on board the vessel was accounted for and 31 people were taken from the scene to a place of safety.
It added that 22 people were taken to hospital, but their condition was not thought to be serious.
The Liverpool Echo reported that another Yellow Duckmarine tour bus sank in the city dock in March this year. Nobody was injured in that incident.
Steve Graves, a reporter with the newspaper, told Sky News: "A number of the ambulances have gone to the Royal Hospital A&E department with people inside them.
"We believe there are people who have been treated at the scene as well. This is the second of these craft which has gone down within the last eight or nine weeks or so.
"The previous one sank without anybody on it but it was a very quick process at the time."
It is understood that some of the passengers had to be treated for shock but that no other major injuries have been reported.
Speaking on Twitter, the Mayor of Liverpool Joe Anderson refused to be drawn on the future of the yellow vessels until he knew everybody involved in the latest incident was safe.
Mr Anderson later tweeted: "Albert Dock incident: police confirm 31 people entered the dock, 31 people have been accounted for. Everyone ok, some people still in hospital."
In May, the Queen had a ride on one of the yellow Duckmarine buses when she visited the region as part of her Diamond Jubilee tour to celebrate 60 years on the throne.