A self-lubricating water-cooled piston-style water pump has a unitary pump housing with a crankcase in direct water communication with the water pump inlet. A low pressure chamber is in direct water communication with the crankcase. A compression chamber is in direct pressurized water communication with a high pressure water manifold through a one-way valve. A high pressure water pump outlet extends outwardly from the manifold to the exterior of the housing. A crankshaft is connected to a connecting rod and a plunger rod, both of which are lubricated and water-cooled in the crankcase. A compression plunger has water channels therethrough connected to the plunger rod and in water communication with the low pressure chamber. The plunger is reciprocal within the compression chamber. A second one-way valve is on the plunger in the compression chamber to let water into the compression chamber.