Sir, - The notion that the building of the proposed marina in Dun Laoghaire would have a "dramatic negative impact" upon the harbour, as stated by Mr. Peter Pearson and quoted by Frank McDonald (The Irish Times, February 3rd) seems so irrational as not to be taken seriously. Does Mr Pearson really think that the harbour was built for any other purpose than as a service area and refuge for vessels? If he does, then let him say what other function its original designers and builders had in mind."The unique quality of the harbour is its large expanse of sheltered water, embraced by stone piers which are without parallel in Europe," he said. But the fact is that at present the harbour is being under-utilised because its builders were unaware of the requirements needed later for the protection of a much greater number of craft. And it is precisely the "large expanse" of water that has made the harbour dangerous in storms to the cost of vessel owners.To talk of views from the harbour being changed as a result of providing the 680-berth marina adds ridicule to the comments, especially as that ignores the urgent needs of boats on the east coast and visiting craft. Strollers and dog-walkers are not to be denied their need to exercise, but vessels must have sheltered water. - Yours, etc.,Frances O'Shaughnessy,Dun Laoghaire,Co Dublin.