As a very young man I worked at a car dealer after school and weekends, washing and detailing cars. One of my peers was the lot boy, moving cars between sales locations and doing tasks such as ensuring the fluids and tires are full. The first time he was asked to top up transmission fluid, he somehow worked out that the brake fluid reservoir was the place to pour.....
Never underestimate human ignorance. The water in the oil may be from a well intentioned but ill informed dealer employee.
