From Longman Dictionary of Contemporary Englishwalk the plankwalk the plankTTWFORCE somebody TO DO somethingto be forced to walk along a board laid over the side of a ship until you fall off into the sea, used as a punishment in the past → walk
Examples from the Corpus
walk the plank• The signal was for Mr Amato, 61, to walk the plank.• Both are completely geared to novices, with plenty of other distractions if walking the plank doesn't suit.• Keel-hauling, walking the plank, that sort of thing. 