Hundreds of people using boats on the River Hamble in Hampshire will now have to pay for the privilege.
Until this year, only sailors that kept boats on the river or that used visitor berths paid harbour dues.
But now all boat-users on the river will have to pay an annual charge based on the size of their vessel.
Those using the river for a short time will have to pay a fixed daily charge. Small boats, safety boats and boats operated by charities will be exempt.
It is hoped the new changes - that will affect about 1,500 boats - will generate about £10,000 a year for the River Hamble Harbour Board.
It will be spent on the costs of managing the river and its environment.
Tim Knight, chairman of the harbour board, said: "This change will bring the River Hamble into line with most other similar harbours, and will mean that everyone who uses the river will pay a modest sum towards the cost of its upkeep."