Mensa Question

Try as I might, I can't make any sense or see the point of this official stencil on the wall of the student residences at Fountainbridge.
It looks like one of those Mensa questions that separate the sheep from the goats and if so, I have failed miserably. Perhaps those Mensa members amongst the blippers can elucidate, knowing that the flats back on to the Union Canal, accounting at least for the introduction of Life Buoys.

It is Burns Night today and the vegetarian haggis is ready for the microwave. Together with chappit tatties and neeps, His Lordship and I will dine royally tonight.
It remains to see if whisky makes an entrance. Me? I might manage a Baileys on the rocks.