RAF BOWMORE
There are three buildings around the edge of Loch Indaal on Islay. I have asked various people what was their function but I have never received a satisfactory answer. I am sure they have some very trivial use but I would be interested to see any suggestions.
I don't think they were intended for boats to be based there as there is a harbour only a short distance away at Bowmore and a pier at Port Charlotte.
My theory is that they might have been something to do with landing lights, buoys etc in the loch.
RAF Bowmore can be seen briefly in the wartime film "Coastal Command" which is available from DD Video.

This is at the head of Loch Indaal alongside the Bowmore to Bridgend road. There was an AA site near here according to CANMORE so they could have held ammunition though I would have expected something more substantial for that.
There are two rooms alongside each other, they probably originally each had a door or opening at each end though one has been blocked up. The building seems to have been well ventilated.