hm. strange...
water is not a hydraulic fluid, it doesnt compress much. injecting water will raise the compression ratio, but the only way i would imagine it doing major harm is if you REALLY sucked in some water... a small amount (like im picturing) would get dispursed into all 8 cylinders and wouldnt be enough to cause harm. but... now youll have the opportunity to open 'er up and check it out!