The number of people visiting the National Maritime Museum at Falmouth has fallen by 20%.
More Cornish history exhibits will be introduced at the museum
Managers say they intend to include general Cornish exhibits to draw more visitors to the museum.
Officials say the fall in numbers was expected, but nearby businesses say they are disappointed in the fall in the number of customers.
The museum's director, Jonathan Griffin, says calls have been made to make the attraction less boat-centred.
He hopes to include more Cornish vessels and history in its next exhibition.
The museum was officially opened by the Duke of York in March, and was the venue for the launch of the Queen's Golden Jubilee tour in May 2002.