Is your water level staying 8' deep? If so and all they did was dig a hole and it stays full, then you could try renting a skid steer for a weekend and see how much bigger you can make it and if it will still hold water.
Yeah, it has held water and never dropped once. I'm pretty sure there's a spring in the bottom of it, or at least that's what the felon/scammer/A-hole told me. It's just really muddy due to the surrounding terrain being exposed dirt/clay. The skid steer isn't a bad idea, of course, I've never operated one before. I'll see how my finances are in 6-9 months and maybe have a plan put together for a new fall dig.
@RAH, thank you sir. As you know, my ultimate goal is to be able to raise blue cats and the hole I have now is too small for that.