On one of my dads old boats that had a 4.3L V6 one of the exhaust manifolds failed and water came in through the exhaust, into the engine, locked it up, also got milky oil. New exhaust manifold, few oil changes, and it was good to go. So I think it's possible to get water in oil through the cylinders.
Most of the time when a head gasket fails or heads warp you get combustion going into the cooling system (high to low pressure). Then you get air pockets in the cooling system which causes overheating.