Polishing non-rock objects and random ramblings

Only other thing I can think of with bubbles like that would be bread, and the epoxy is dyed yellow.

Maybe it is grilled cheese sandwich.

The yellow foam padding like that is used on top of beds?

Not yellow foam, bread, grilled cheese sambo or Corian either! :-) Some cool guesses there! Can tell you that once you know what it is you will never unsee it! :-) Will let it float another day or so, see if there are more bites...

Nope, not dyed pumice either! On my early morning walks part of my walk is on a bicycle track around Mushrif Park, and the guys had done markings on the tar track a couple of years ago. It is hard-set yellow road paint they had spilled next to the track! :-) You can see the little reflective balls and voids for the balls in it.