In the science fiction movie, The Abyss, a diver is able to breathe while his head is immersed in a specially prepared liquid pumped into a water-tight helmet attached to a suit, thus allowing him to dive without an air tank and at greater depths than possible for scuba divers. Is this purely fiction, or is it at least theoretically possible? Explain, considering the nature of alveoli and alveolar gas exchange. Assuming it is possible, describe the composition and nature of the liquid in terms of its oxygen pressure and concentration

This type of experiment was carried out in 1960s on rodents, it was partially successful but was perceived impractical and dangerous for humans,it is possible theoretically.

Oxygen is broken down or dissolves in a thin film of fluid in the alveoli, surprisingly in normal breathing liquid composed of dissolved oxygen is involved. Evidently respiratory gas must be able to dissolve in this liquid and in concentration required to keep the partial pressure necessary to power diffusion.