As Paul says, they will find a way past any barrier, it seems. My pond has been relatively safe from raccoons only because it is deep and straight-sided. They need a place to stand so they can fish effectively.
Your pond looks like it would be steep and deep enough, but if you have your submerged plants like water lilies at a convenient level they can stand on the pots in the pond. They can't fish if they are swimming.
I'd recommend planting tall water plants like Cannas, iris or Elephant ears. Stand the pot on a cinder block in the middle of the pond with the top of the soil just barely submerged - an island with steep sides! Very quickly the pot will be so full of stems there will be no place for the 'coons to perch. The cinder block tunnels provide a little bit of a hiding place for the fish, too.
Shame to have to give up on the water lilies, but unless you get big ones that can be deeper, you'll keep having the problem and spend a lot on plants. And of course big ones would quickly get too big for the little pond!
Combine that with a Scarecrow motion detector sprinkler and maybe they'll be discouraged.
