Water does not “explode” in the same sense than a explosive substance does. What happens, If you pour water into something burning at a high enough temperature, on one side it changes phase rapidly upon absorbing heat, and a fast phase change can be called “explosion”, but if the temperature is high enough, it will also cause thermal lysis of water Molecules into hydrogen and oxygen, that then recombine again, and there you have a real explosion, but it’s not water exploding, but it’s hydrogen burning at the fast rate it does to form water again. If the source of the high temperature remains, this can happen again and again, so, water is not the way to put down high temperature fires. Anyone remembers Fukushima’s nuclear plant explosions? Those were from water contacting the runaway hot nuclear fuel, becoming hydrogen and oxygen, and exploding.