My mind saw something looking like it might be a diver...perhaps triggered by the upright inflation-pipe fro the float-collar which looks like a snorkel tube.
But on a subsequent look, the yellow object appears to be the right-side sole of a pair of yellow-soled footware, possibly near the cocked right knee of Fuddy.
Lying back in the water with her feet toward the camera but angled to the viewer’s left, Fuddy may have cocked her (quite obese) right knee creating the impression of the back of a divers head thus lifting the toe of her right yellow shoe briefly out of the water.
Then she extends the leg straightening it out to her right causing the knee to descend into the water and the toe of the yellow shoe to move towards the viewer’s left.
Yes. She’s probably kicking her legs to move about.
In that scenario where is Fuddy’s head? Which way is she facing?
Fuddy’s shoes were all black.