Mine do the same they absolutely love digging in the mud when I dump my pool. That one looks pretty nice, how solid are the sides of it? They kinda look like just fabric
It's a heavy mil vinyl that is segmented with a thick MDF type board inside. It helps give the sides some stiffness so they don't "fold over" if pushed on from the outside like you might see with some kiddie pools. I put a tarp under mine since I had some stout woody weeds I had cut down and I didn't want it to puncture the bottom.... But I haven't had any problems with leaks or anything. The pool has made it 8+ months so far like a champ. I fill mine about 9-10 inches deep. Enough to cover the top of the concrete block I have on the inside to help them climb out....

