The term hydro means "water" and "lock" means to close of from. In this case, the water closed off his ability to turn over the engine to start his car. There are many different cases of Hydrolock. Your situation (cooldude) is one of the worst you can experiance. My uncle is in the Marine business. He restores sunken boats and water skis (don't know how those sink). But many of the motors that he restores are still in working condition. He just pump it filled with ATF or any cheap petroleum based product and crank it until you can see ATF coming out of the Oil galleries. Then he sprays down the motor with Water Displacement 64 (WD64) to stop any more damage from water on the motor. That was a good idea changeing the oil, I never remember that until now.