Which? blame this, in part, on the fact Saga charters its ships.
With that said, the line is due to launch its first river cruise ship in 2021.
Express.co.uk reached out to Saga to get their take on the survey.
Other mahor brands included in the 2020 survey were AmaWaterways, Riviera Travel, Saga Cruises, Scenic Luxury Cruises and Tours, Emerald Waterways, APT Luxury River Cruises, Uniworld, and Viking River Cruises.
