If this were the case it would be running very hot very quickly dixibell.
Water entering the cylinder under radiator pressure would mean compression and firing pressures that are many times greater) blowing back and blowing the water out of the radiator cap.
The other scenario is a crack between the water jacket and a valve seat (usually exhaust). In this case water is seen to be dripping from the exhaust, and blows out in a spray when revved. Coolant loss would still be very noticable.
