Windermere ferry will be out of action for three weeks, for essential maintenance work.
The Mallard transports tourists across the longest lake in England - between Bowness and Far Sawrey - and can carry 15 cars, and more than 100 passengers.
Every five years, the ferry needs to have an out of water inspection to make sure the vessel is fit for the job.
The work, which is is costing around £150,000, will include the installation of a new access platform from the side of the vessel to the car deck, making it safer in the case of an emergency.
It will be out of service from March 4.