Sailors stopping off for the night can moor up safely then pay a modest sum for the privilege.
The proceeds from that honesty box go to the primary school just up the hill, funding off-island trips for the children.
There are mooring buoys off the Isle of Rum too. Both the pontoon and the moorings were provided free by Mowi, the salmon farm company which has a farms off the shores of both islands.
The company insisted it would take no income from the infrastructure it provided, preferring the money went to benefit the local schoolchildren instead.
Mowi has also provided two house plots on Rum, all serviced with electricity and water, which will soon be handed over to the local community.
There are similar stories on nearby Colonsay which has also benefited from Mowi's investment. The company's work on all three islands has brought everything from broadband to help in transporting building materials.
This is the nature of 'social licence', the contract salmon farmers have with the communities they operate in. Some of this social licence is unwritten and offered by the companies because they know what the communities need.
Other parts are actually contractual and are written and agreed between communities and companies as a condition of building a salmon farm nearby.
Salmon farmers know they must be good neighbours to those who also work the marine environment in which they operate but they must be good local employers too.
And it is because Scotland's salmon farmers understand this and live it through their operations that islanders on Muck and Rum and Colonsay all voted for them to come in.
But this is wider than just putting in pontoons and providing employment.
Last month (August), four new houses in Ullapool were handed over to employees of Wester Ross Fisheries.
Wester Ross, Scotland's smallest salmon producer, knows that the biggest barrier to recruiting and retaining staff is housing.
Gilpin Bradley, the managing director of Wester Ross Fisheries, said: "Houses are generally unaffordable for young people moving to the area, both in terms of the rent - because holiday homes have driven up those prices - and for those who want to buy.
"That's why we took the decision to buy these houses and provide subsidised accommodation for our employees."
Similar tales are heard all over the sector. Housing is a real issue on the west coast.
There is not enough affordable housing and the stock that does come available on the open market is usually snapped up by people looking to run holiday homes or by retirees.
Remote working and the spread of good-quality broadband has also had an impact. People who might have been based in the central belt in the past can now work in the Highlands and islands, perhaps returning to their urban headquarters once or twice a month.
Salaries in the salmon sector are good but, for young people starting off in the sector in the most popular parts of the west coast, they are often not good enough to even think about buying property, particularly if the competition comes from cash-rich retirees moving up from the south.
With the rental market also skewed by the holiday home businesses, having somewhere decent to live is the biggest challenge facing those trying to start out in the salmon sector.
Then there is broadband. These days it is unlikely that anybody is going to take up a job in a remote area without it.
That is why Scotland's salmon companies have been so pro-active in providing this service.
Last year, Scottish Sea Farms worked with broadband provider HebNet CIC to install superfast cover for the residents of the remote Knoydart peninsula and Loch Nevis.
Salmon farms need it to connect the barges to onshore hubs and this has often been the catalyst for the companies to roll it out to the community at large.
Opponents of salmon farming often like to portray Scotland's salmon farmers as faceless, foreign-owned corporates with no connection to the local communities they operate in.
They could not be more wrong.
Salmon farmers know they need the backing of their local communities, whether this is explicitly - as in the cases of Rum, Muck and Colonsay - or tacitly, in the case of most other parts of Scotland.
In fact, they would not be able to exist, let alone thrive as part of their local communities if they took no heed of the social licence obligations they are under.
They know that community involvement is not just a box-ticking exercise and that providing jobs and boosting the local economy is no longer enough.
Sometimes this takes the form of sponsoring a local football team or providing prizes for a tombola.
But, increasingly now, it can stretch as far as free moorings for yachts or even a clear route on to the property ladder for local employees.
This is social licence made real and the visiting sailors who drop a few quid into the honesty boxes on the end of the pontoons are a key part of that - whether they realise it or not.
This article by the SSPO's Hamish Macdonell first appeared in the September edition of Fish Farmer magazine.