AT THE PROPERTY I INHERITED FROM MY LATE PARENTS, there is a backyard swimming pool. It's large (20'x40') and in-ground, though there was some contrivance to achieve that.
The back yard slopes down as you go back, so the concrete pool was built partly above ground, then surrounded by a cinder block wall, forming a space that was then filled with dirt and topped with a concrete deck. Any fool should have known that that fill dirt would settle, leaving the concrete without a foundation. Then the concrete would crack and buckle and become dangerous to walk on. Which is what happened.
And so the pool fell into disuse and neglect. In the summer it became a green frog pond, giving off a chorale of trills and croaks every night. I got tired of having a swamp in my back yard, so I finally set about to clean it. At first I used a leaf net to dredge several inches of algae and frog carcass muck from the bottom, which was tedious and damaging to the leaf nets that weren't designed to carry 25 pounds of slime. So I filled it up and used a pool vacuum hose to siphon out the rest of the muck on the bottom. (The peculiar partly-above ground design with the retaining wall allowed siphoning; otherwise I'd have to use the pump, which would have required me to empty the skimmer strainer every minute or so.)
I dosed it with algaecide and shocked it with chlorine, I vacuumed, I brushed, backwashed, and netted, and after a week I saw that it was good. It took a lot of work. Now I can stand there and see the suction grate nine feet down in the deep end through crystal clear water and you know what? I grin. I feel good (you know that I would, now). I rejoice.
The joy of building something good. Fixing something that had long been a burr under your saddle. When you can stand there and admire what you've done. That's good livin.
Now, the concrete deck will be a taller order. But we'll see about that.