Sunday Solution

Here's the whole story of the puzzle. First, the original sighting, where I noticed something a little unusual.

I had been looking at the duck feather floating in the water, trying to figure out whether it was mallard or wood duck (mallard, I think) when I noticed a movement in the duckweed. Or, more precisely, a movement of the duckweed. I watched it for a long time as it inched along in its green camouflage coating, waiting for it to reveal itself. (As you can tell from picture #2, it's just to the right of the middle plant.)

Here's #2 - a closer picture as it continued to move around and you can see that there's something starting to emerge.

And then, in picture #3, off to the left of the rising, domed shape, there's something elongated coming to the surface.

Finally, the little rascal raised its head for an infusion of oxygen. I love how the duckweed still clings to most of the head with almost just its eye peering out of the green.

It gave me a thorough inspection, coming fully around to see who was peering so intently in its direction.

Then, deciding I wasn't any threat and of very little interest, went on its way, disappearing back into the cover of duckweed to feast on whatever it had been finding beneath the surface. 

I see painted turtles far more frequently sunning themselves on logs or rocks, then sliding into the safety of the deeps (or shallows) when disturbed. It was fun to watch this one going about its more active (though still slow) daily rounds.