It won't explode, except at a micro level.
If the bowl is made of brittle material that somehow didn't melt at 620C, then it might shatter when dunked in water.
Dunking heated metal (for instance Steel) at 800-900C into water is how you make Martensite (harden it via heat treating).
If the bowl is made out of steel for instance, it will do nothing but just harden the steel.
tldr: Its reaction depends on the material, none of which are explosion if there is no chemical reaction.
This post was edited by Dontrunaway on Feb 14 2014 10:52pm