For me it reminds me of the LCL in anime series Evangelion. I have seen it pop up a few times in modern sci-fi.

Same. NGE is actually referenced in the "Fiction" section of the wiki entry, along with others.

I seem to remember this being in the book "The Sphere", though I might be wrong. I actually always thought that it was something rarely-used-but-possible.

The overlap between close-to-current sci-fi and real life in my brain is occasionally saddening/shameful.

Interstellar seemed to suggest use of a similar method when the astronauts were in hibernation.

Although I am wearing a scifi hat, not reality, assuming they don't need to breathe in hibernation, the full fluid immersion is probably a good way to regulate internal body temperature.

This is why I posted the link. I never realized the liquid was real and that the scene was shot using it. After watching the scene I thought, did they drown that rat? Effects were good, but not that good!