Originally Posted by
NutLoose
Not as outlandish as it sounds.
For
the anti-submarine defence of UK ports, harbours and anchorages during the Second World War, sailors in rowing boats were equipped with pairs of binoculars and pots of green paint. When they spotted the periscope of a U-boat, they rowed over to it and painted its lens with the green paint.
The U-boat commander, thinking he was still below periscope depth, would keep trying to ascend. By the time his submarine had risen a couple of hundred feet in the air, it was easy to bring down with anti-aircraft fire.