I interpreted it that the plane dragged the wire in the sea in front of the minesweeper in the heading of the pilot. This would have drawn a line in the sea, as it were.
That would be a totally unexpected behavior, which would give the minesweeper's captain the clue that it was a signal to change course to the given heading. The plane would have headed back to the pilot and circled, giving the minesweeper's captain assurance he had understood the signal.
That would be a totally unexpected behavior, which would give the minesweeper's captain the clue that it was a signal to change course to the given heading. The plane would have headed back to the pilot and circled, giving the minesweeper's captain assurance he had understood the signal.