A super soaker is a great deterrent. I used one on an irritating squirrel and a few of the local cats. The thing is you don't need to hit them with the water just get close and they run away. After a few 'shots' I just had to go out with the soaker in my hand and they'd run even before I aimed it. Now I just have to go out and clap my hands and they make a bee-line for the fence.
I found the drinks bottles filled with water stopped a fox, who visited regularly, from trying to dig under the fence wherever they were placed and now I have bottles going down both sides of the garden at the back of the borders - I'm not moving them just yet but there's been no signs of a fox for quite awhile now.

But whether it's cats or foxes they do make a mess and cause damage to the plants so I don't want them either, but there's no simple quick fix I'm afraid - but if you find one let us know.

Jan