i dont think, there is a good argument for smoking hookah, you can tell your parents ...
smoking is bad - doesnt matter if its hookah, cigarettes or something else. hookah is bad for your health, too ... but its maybe less harmful, than smoking cigarettes.
well, since i am 18, my parents dont care about it anymore. my dad doesnt like it, but he cant treat me like a child. so he stopped banning my hookah from his house
when i was not of full age, i just went out for smoking (friends, bars or so. and in summer we were smoking in the garden)