Water drop BS?

I once heard a man talking about somthing he called a water drop system. He swore that his brothers car (a m3 i think...) would gain rediculous amounts of hp by using water in a similar way as a nos system. I am sceptical about this as in my mind water in an engine has always been bad...has anybody heard of this or somthing close enough to it that he could have been confused? your thoughts...

Water in mist form can be used to clean the cylinders ( a.k.a. pots) while the engine is revving at a moderate pace. However, I don't think water can be used at all when the engine is at full rev.