It is a z-axis Pike Visualizer for the Prusa Mini. Designed to show when the motor is spinning. Best printed with supports across the bottom.

Update1

Just uploaded a Swimming Pike version. Still experimental. 

Update 2:

I have finished a new version of the swimming Pike. Now it is chasing a yellow perch. Works great and image showing it printed out. Needs full support to print properly. Fin on the perch is finick to print.