Just happened to me.
Was fishing on Deimos with the first spear you get from Daughter.
Jumped to melee a Gravid Blastema that fell in the plasma and did not burst right away as they do when falling.
Hit it with the spear and it just happened!
Can't do anything with the character but Aim and turn around with mouse movement.
Tried /unstuck. It moved me to the "shore" of the plasma river but remained the same. Now I'm there not being able to kill myself and questioning my life choices. Do I try something new? Do I lose all of the time I've spent in the free roam sinc