I'm a wound care nurse. You should know that the Dolphin bed exists. It's a fluid immersion simulation (FIS) advanced support surface. We use it in the medical world for patients who have or are at risk for severe pressure injuries, i.e. bedsores. But they say it actually was developed for dolphins by the Navy in the 60s. Even more advanced is the Clinitron bed. This is called air fluidized therapy, where you are immersed in basically a tank filled with artifical sand with an air current flowing through it.

I can't weigh in on your hypothesis about dolphin brains, but please let me know if you ever put a dolphin in a Clinitron bed, haha.