Bobeana (boe-bee-nah) got out of her pool and I spent over seven hours looking for her. Eventually I decided that she got out of the backyard, and I went back to her pool to empty and store it. I heard something hiss at me, and I turned to see that she was stuck like this. Thankfully the wood kept her in the shade, so she's still alive.
@Shakudo I'm thinking she climbed up the chicken wire, and when she got to the top she fell down the other side, getting herself locked between two fences.
I thought she learned her lesson the FIRST time, when she climbed up the fence and slipped, getting herself stuck between the chicken wire and a tree.
But noooo.
Now I made it just about impossible for her to escape from her tank xP