uh... usually you would sanitize something like a turkey baster to draw a sample and put the hydrometer sample tube in the refrigerator.
anyways--- the target OG was likely in excess of 1.065, right?
if your current gravity is a lot higher than 1.065, then yes I guess you could dilute it. If it is lower than the target OG, it just depends on whether you want 5 gallons of weaker beer, or 4 gallons of the "right" beer. my two cents.