The river enthusiasts regularly block the car park of the Cornstore Emporium at Swan Bridge in Pulborough, preventing customers from getting to the shop.
And, says owner Helen Johnson, they regularly use the tea rooms’ sole bathroom as a public loo and changing room.
“This is our car park and our neighbour’s drive, not a drop off point for the river,” she said.
The car park adjoins the river slipway and, said, Helen: "We appreciate that the slipway is access to the river but every time this happens it is killing our business by stopping customers getting to us.
"I employ 10 people and have 30 other stall holders who rely on the income from this business – a business that has been established for 20 years.
“We have worked harmoniously with river users for the majority of this time but recently this is just getting beyond a joke.
"Not only are we a local business but an important focal point for our village,” said Helen, who has worked at the Emporium since 2006.
"In the past few years we have helped find a missing runaway child, reunited a confused elderly lady who was lost, stopped a drunk driver from causing a serious crash, helped a young man who was being abused in the car park, and most recently helped a stranded family of river users that had mislaid their belongings with the use of our CCTV .”
She said people often said they were ‘just dropping off’ but "that isn’t a good enough reason when you’ve heard it for the umpteenth time that day.
"With a lot more consideration we can all enjoy this beautiful location that we have.”
She said she had put up new signage but “they don’t take any notice of it.”
She added the canoe and kayak tour agency Fluid Adventures, which uses a car park on the other side of the bridge, had tried to work with them.
“The majority of issues are caused by the constant stream at weekends of people ‘just dropping off’ and ignoring our signs,” she said.