If there was water in the oil still in the engine. That is a rather critical bit of information. If the Oil has no water in it then he doesn't have a leak of coolant (raw water or anti-freeze) into the crankcase. In that case the most likely problem is a bad oil seal somewhere. If the oil is cloudy then he has water in the crankcase and most lileky has a a corrosion problem that generated a hole between the cooling passages in the block and the crankcase.

Water pumps seldom leak water into the engine because the oil is at higher pressure than the water