Most impressive case of someone making their engine go hydraulic was about 8 years ago at work. E32 750iL the bloke had driven into deep standing water and the engine must have sucked up enough water to put a pint down each cylinder. Needless to say the engine shat itself hard, 4 pistons complete with mangled conrods were spat out of the block. Two exited through the sump the other two went out sideways, game over, water 1 bmw 0.