While sleeping underwater, I naturally couldn't breathe. But then again, I'm not a normal human being to begin with. Although being unable to breathe was definitely uncomfortable, I had somehow grown accustomed to it over time. After spending weeks here, I guess you could say I sorta got used to it, so it didn't bother me as much anymore.
Based on the taste of the water here, if I had to describe it, I would say it was unpleasant and very sour. In short, I knew for sure it had an acidic taste, and I could feel my mouth burning slightly. Fortunately, my body was strong enough to handle the acidic water, and all that thanks to my high level as well as my regeneration skill.