There is a place which serves hookah, and the shisha that comes is flavoured, and contains no tobacco, no nicotine and is filtered through the water. Is this harmful at all?

There r very few ''herbal'' hookah bars.

l would ask them what brands they r using, The only Herbal brands are:
Soex, High-Life Smoke, Saalaam, & Hookah Hookah Black Label.

There r no studies on it because they r no studies on herbal smoke. So treat it as the same as tobacco. Not healthy but only a fraction of the damage cigarettes does.

Some bars will say it is just molasses. Most of these bar owners r stupid & usually get shut down because the will use a brand like Sallam Moassel or something that says Hookah Molasses. It still contains tobacco.

Here is a link to familiarize yourself with Major Hookah Tobacco Companies
http://hookah-shisha.com/store/pc/viewCat_h.asp?idCategory=3&idaffiliate=284