@chauhdarywaqar
simple principle, cars suck in air, inject fuel, compress it and it burns. but when the air intake has water ahead/inside it it forces water into the cylinders and as we all know "water doesn't compress like air does" so usually the first thing to go is the connecting rods.
if this guy is lucky it's only a matter of replacing the rods, but if not it might mean a bent crank shaft or worse.