That's fricking horrifying

"Infected snails may survive for at least a year and continue to be able to use the eyes on the ends of their tentacles."

The video showing how the worm mimics a caterpillar's movement is wild! Also a bit terrifying...

This features in a scene (episode 9-ish) of The Trials of Life, the Attenborough series from 1990 that has tons of pathbreaking camerawork. It's all now free to watch and still holds it own against the more modern BBC stuff.

https://en.wikipedia.org/wiki/Trematoda?wprov=sfti1#Intestinal_flukes