I dropped the boat on that one

This is a terrific congruent conflation of “missed the boat” and “dropped the ball”, both meaning to have made an error or mistake.  Maybe the speaker was experiencing an earworm of that 1974 song “Rock the Boat” by the one hit wonder group Hues Corporation.   In any event, this double whammy can be used to describe the mother of all mistakes.  A big thanks to Marcia Riefer Johnston who sent this one in and is a new malaphor follower.  By the way, she has a great website, http://writing.rocks.  Check it out!