Advice re a small wildlife pond

I'm not quite sure what to do with the edges. what would you suggest please?
I did see your recommendation about sloping the edges and have tried to do that but the bath had sloping sides and it was difficult to back fill around the hole.

 

It's difficult to get a perspective but it looks as if the area behind it is considerably higher. If so, this might cause a few problems.

There's a number of options, small paving slabs, or as I have crazy York stone, or more in keeping with a natural pool, half buried cobble "sets." You could diguise the uniformity of the pool by not making them completely follow the contours of the four sides.

 

Sorry to hijack the post but I wanted to know how can I prevent cats fro harming the wildlife. I have a cat that visits the garden and before I install a pond I want to make sure this problem is sorted.

 

Depends on the cat I s'pose, but most cats are more "watchers" than "catchers." In the "real wild" the wildlife have to take their chances.
I don't think there's much you can do to control cats.
That's why there's never any job vacancies advertised for "cat shepherds."

 

I have to agree with Doghouse Riley. There is no easy 100% way to stop cats from doing anything, so as Doghouse Riley also says, anything will have to take its chances.