won't hold water

not hold water

To not be or not appear to be true, verifiable, or able to be supported by facts. The image is of a container with holes in it—a metaphor for a position or argument containing "holes" (errors or gaps in reasoning). I'm afraid that excuse just doesn't hold water with me—you still should have had plenty of time to complete the assignment and print it. That old claim has been debunked so many time that it just does not hold water any more.See also: hold, not, water

won't hold water

to be inadequate, insubstantial, or ill-conceived. Sorry, your ideas won't hold water. Nice try, though. The prosecution's case wouldn't hold water, so the defendant was released.See also: hold, water