Cost per nautical mile, what a mile on the water really costs

Nine thousand euros a year over three hundred nautical miles comes to thirty euros a mile. Spread the same costs over a thousand miles and you pay nine. The figure does not tell you whether a boat is expensive; it tells you whether it gets used.

For insurance, this raises a practical question: owners who go out rarely pay the most per mile and gain the most from the seasonal policy, which charges a premium only for the months the boat is actually in use. Owners who go out often, by contrast, should look at the extent of cover rather than at the premium, because the likelihood of a claim rises with frequent use.

The premium itself is the smallest item in both cases. Out of nine thousand euros a year, typically less than a thousand goes on insurance; berth, winter storage and maintenance make up the rest. If you want to save, those are the items worth working on.