A player of mine who is just looking into the Dresden Files had this idea:Drying out?
The Blue Court.
As for what kind of Catch they could have, that I'm not sure.
Drying out?That may be an environmental thing, but I mean, if you're near water there's not much you can do. Catches are typically, well, combative things.
Seriously - They need a supply of water. Thus they could only function in 'damp' climates - near the sea or lakes, or places where it rained, or there was a supply of running water (Most cities would be fine due to Taps and Baths etc)
If they're marine, though, salt might be good for them; fresh water might not be, though.