WATER IN IDIOM
A flawed plan will hold no water; a plan that is exposed might be dead in the water, or risks being blown out of the water; whereas a plan that will stand close scrutiny is watertight--unless someone pours cold water over it. (And even if they do, it might just be water off a duck's back.) To carry water to the river is like taking coals to Newcastle, and while you can lead a horse to water, you can't make it drink. If you have muddied the water, you might seek to pour oil over troubled waters; a true friend will seek always to be a bridge over troubled water. If you fail to keep your head above water, you may find yourself in hot water or deep water (not forgetting, of course, that still waters run deep). You may not take to a backwater like a duck to water--indeed, you may feel like a fish out of water. However, since much water will haveflowed under the bridge, it is advisable simply to tread water and avoid the temptation to throw the baby out with the bathwater. Remember always that blood is thicker than water, come hell or high water.
"James swerved to avoid running over the hotchi witchu."