Royal Air Force Chiefs were amazed at the 100% success rate that the Irish Air Force Anti-Submarine Hunter Planes achieved in WW2 shooting down submarines. When the 30 year Rule was allowed the files got "misplaced" until recently discovered buried near a cess pit in Southern Ireland. Apparently, when they detected that a Sub was nearby they would pour 45 gallon drums of blue and green paint over the side.
This, being oil based, would form a thin film on the water, and when the U Boat Commander went up to periscope depth, the blue and green paint would smear across the periscope lens and the Commander, thinking they were too deep, would call out "go up another fifty feet", and when they were 300 feet in the air the Irish Air Force would shoot them down.
This, being oil based, would form a thin film on the water, and when the U Boat Commander went up to periscope depth, the blue and green paint would smear across the periscope lens and the Commander, thinking they were too deep, would call out "go up another fifty feet", and when they were 300 feet in the air the Irish Air Force would shoot them down.