What causes water to get into the cylinders on 2003 Lincoln Aviator

My Aviator is currently at the dealer for repair. They've indicated that there's water in the cylinders and the coils, spark plugs and gasket need replacing. What would cause water to get into the cylinders?

Asked by for the 2003 Lincoln Aviator
The head gasket must have failed and you can view this estimate here put in your vehicles info and choose head gasket replace