Help ID this critter

[Prevailing Reef]

It’s tiny, very difficult to see with the naked eye.

 

[DaJMasta]

I'm not sure you've totally found focus on it and the seeming texture of the background of the image seems oddly rocky (not generally a look microscopic things have).

Do you have an estimate of how big it is? What shape it has (by eye or magnifying glass?) What behavior it shows? Where was it found?

And for using the microscope, how did you 'prepare' it - like, did you put it on something, what is the lighting like, etc.?