All the pulleys, tensioner, and idlers are in the same plane on a serpentine system, so the water pump shaft will be in line with the crankshaft pulley. That's about as "short" as it can get. The only reason for a longer shaft on the water pump would be to align the pulley with an extended sheave on the crankshaft. Some V belt systems have two or even three layers of belts.

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Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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