Developers of a proposed £14m Anglesey marina fear their plans could be sunk by a planning move.
An aerial shot of the proposed development site in Beaumaris
An application has been submitted by Beaumaris resident Howard Mattocks to register the area under "village green" status.
This would protect the recreational area and 100-year-old fishing huts which Mr Mattocks claims could be lost.
Developers, the Anglesey Boat Company, says this could scupper the 450-berth marina and plans for 150 new jobs.
The company received planning permission from Anglesey Council earlier this month for the Gallows Point development.
Mr Mattocks, who owns a unit which restores and repairs old boats at the marina is concerned old fishermen's huts there, dating back 100 years, will be lost.
"I don't want the development to fail," he said. "But this is a modern development of industrial type units which I am totally opposed to.
"It's not in character with the town of Beaumaris."
Mr Mattocks said he was receiving assistance from the Henley-on-Thames based Open Spaces Society - a conservation group founded in 1865 to protect common land and public rights of way.
An Anglesey Boat Company spokesman said the application for village green status on the site of a boat yard and petrol station was "vexatious."
The company owns a boat yard and chandlery on Gallows Point employing 18 people.
The spokesman said: "Anglesey has got higher unemployment that almost anywhere else in Wales.
"We have the highest loss of young people who leave the island because there are no jobs and we are trying to create highly skilled engineering jobs."
The developers already have the go-ahead for a marina in Fishguard
The company, who were given the go-ahead last year for a £10m marina at Fishguard, said the development would generate spending of over £8 million a year in the Beaumaris area.
"We hope it will revitalise the town just like the marina in Pwllheli transformed the economy in the Lleyn peninsula."
Beaumaris' chamber of trade and tourism is also opposing Mr Mattocks' application for village green status, arguing that there is no sound historical basis for it.
Anglesey Council as the registering authority are to consider Mr Mattock's application and have the final decision.
A spokeswoman from the Open Space Society said it was possible the development site could become one of an estimated 220 registered greens in Wales making up 620 acres of land protected by several Acts of Parliament.
Any land not registered by 1 August 1970 ceased be a town or village green.
However it is possible that unregistered land may have 'become' a green if a significant number of local people have been involved in lawful sports and pastimes over 20 years.
If Anglesey Council does decide to register the land as a green, it should protect it from development.