Water has been used to cool steel since the times the smiths make swords and cooled them in water to make them harder. You can simply take out a piece of metal from a 800 degree C oven and cool them in cold water, I have done this myself and the temperature of the metal drops at once without cracking. It will affect the structure and how the metal is composed but it will not make it crack.
There are cars that can run with their engines under water, the engines will not crack, and a believe that at least a few of these cars have turbocharging.
Even if you completely submerge a whole turbocharger it will stay hotter than the water since we add heat to it all the time (we feed the turbocharger with more energy than we get out from the crankshaft). A turbocharger has no rotating parts that are in contact (except the bearings in a ball bearing turbo), and as for the compressor the cooling will only do good.