Okay, well here's a bit of insight, that could be complete BS, but I'll give it to you how I received from someone who could absolutely know. Question is, was he lying.
When I went to commercial dive school the head of the school was a retired Navy Diver that had spent years as a saturation diver and then spent years working at the NEDU in Florida. His knowledge on all aspects of commercial diving was pretty exhaustive. He told us that the diving medium used like what was explained in the The Abyss was NOT fiction. He said that the NEDU had been working on it, that they had successful results with mice or rats and actually had 4 volunteers to try the system out. Each of the 4 volunteers who tried the liquid medium described what they could only assume drowning felt like. Each of the 4 volunteers also stated that they would NEVER do it again. They explained that they were terrified during the experience and truly believed they were going to die.
Anyway, that's the story I got from an old Navy saturation diver and NEDU retiree. I never caught him in a lie, but who know's if it's true or not.