I had an acquaintance who altered it to 'up the proverbial estuary without suitable means of propulsion'. It took most people awhile to get it, including me, the first time. Funny guy.
I recall a scene from The Winds of War where it's during the Battle of Britain and an American observer is there. A British general said that the German pilots gave the English Channel an unkind name, "roughly equivalent to that creek you Americans are always finding yourself up without a paddle."