Swimming is good for me:

Swimming in a swimming pool is good for me. Really. Swimming strengthens so many muscles, with so little strain, and burns so many calories. I have to keep reminding myself about this, especially after today.

I was swimming in my favorite lane, at one edge of the pool. About halfway down the lane, peering underwater, I could see what looked like a small rusty bolt screwed into the bottom of the pool. I don't know when I first noticed it, maybe a long time ago, but I certainly saw it there last week. Today in midlap, I realized that this thing could not be a bolt. There was no imaginable need to make a hole at that place in the pool, nor to screw a bolt into a hole there. So it must be some object lying on the bottom of the pool.

I like to retrieve junk from the pool bottom. I float very well, so to go down to the bottom, I have to do something unintuitive: I expel all the air in my lungs and dive down. I did that and came up with a buffalo head nickel. I have quite a few of these, but the one I pulled off the pool bottom is different: it is almost flat. Somehow, all the embossed detail has been eaten away. Looks like the weird chemicals in the pool have done a number on this nickel, disfiguring it while it lay on the bottom. And how rapidly? I don't want to think about it, because: Swimming in the pool is good for me.