Water Bags repelling fly's

I saw it but couldnt believe it. A resteraunt with a plastic bag half full of water on all four sides of the building.
Owner claimed that it repelled flies. I didnt believe it but luckily found one site that had some reference to this phenomena. An Iowa professor claims that it works after experiments were conducted but still cant find the reason it works.
I wonder if anyone here could share any information on this subject.

See Water in a bag keeps flies away??

What’s the purpose of bags of water hanging in restaurants?

Well, since that one’s been answered before, maybe someone can answer about a similar phenomenon.

Sometime soon after I met my now wife, she repeatedly found paw prints from a neighborhood cat on her car, which was only in the car port at night. She put some water in an empty milk bottle, placed it on the ground in front of her car (all this according to an old wives’ tale she knew about), and voila! Never again was her car marked by kitty paws. This did not surprise her nearly as much as it surprised me.

Any thoughts?