Ah diesel submarines - that takes me back, sailing past the pens at HMS Dolphin, in through the harbour mouth at Portsmouth, Hampshire, UK, then make a sharp left.

There was usually one or more charging up and the du du du du sound of the engines seemed to be carried as much by the water as the air.

I used to sing 'Sally free and easy' to the beat, as that is how it was written, and go on under Pneumonia bridge and pick up the mooring, home again.