Meaning: I don't believe you. Generally used in response to a story that seems farfetched.
------------------------------------------------------------------------------
Living in the US, I automatically connected the 'marines' with the U.S. Marine
Corps. and the saying was not clear.
It turned out that the proverb appeared well before the U.S. came onto the scene
as an offshoot of a long line of naval powers: the Romans, Venice, Spain, and
the British Empire. According to my source, the early Brit sailors who invented
the expression had a low opinion of the marines stationed on their vessels.
