Immotile:
lacking motility
a free-form sculpture that manages to suggest movement while remaining an immotile object [Merriam-Webster]
Noted in the NewScientist Aperture column (22 April 2017):
The place is significant for Barker, for it was here, in 1816, that marine biologist John Vaughan Thompson was posted as a military surgeon. In Cobh harbour, he became the first person to observe the small, immotile organisms known as plankton.
I suppose it should be noted that, in the context of the column, Barbie Doll legs are considered to be immotile.
