Let me build on @AlexP's comment, because he's completely right. You can't have liquid water floating above any atmosphere no matter the pressure because LOX is lighter than water. The water would fall and the LOX rise (and then probably boil into a gas).
But let's explore the idea in a little different way...
Because the idea is super cool.
Water vapor gets up there in the form of clouds, which precipitate rain. Might it be possible to have a dense but breathable atmosphere below that permits a very high concentration of water vapor above? And can that water vapor be dense enough to permit, for lack of a better example, fish?
For the moment I'm going to completely ignore the fact that fish would fall through water vapor for exactly the same reason AlexP described. I'm also going to ignore what happens to the poor suckers when they happen to swim out the bottom of the pond....
Now, full disclosure, I am not by any stretch of the imagination a meteorologist or climatologist. I am officially pulling this random string of barely related thoughts out of not particularlly dense air. You've been warned.... (And if you're tempted to downvote just because my science is off by miles, remember that I'm having a lot more fun than you are. Thbppttt!)
So, you don't tell us who's living on your world, so let's assume some humans have adapted to the climate. According to Wiki the earth is 78% Nitrogen, 20% Oxygen, 1% Argon, 0.04% CO2, some stuff we don't care about, water vapor to between .001% and 5%, and 0.000179% Methane. That's 99.0412% of our atmosphere excluding the stuff I'm not going to worry about and assuming low water content.
It's the Nitrogen that's really killing us. That stuff is thin. So we need to reduce it to something like 45%. It's gonna smell and it's going to be honking hot, but we need to vaporize water anyway, right? Let's up the Methane to 2.5%, the Oxygen to 45%, the Argon to 3%, the CO2 just a smidge to 0.05% and up our water vapor to the range of 2.5% - 7.5%. Take those elements I'm not caring about and up them appropriately to fill in the gap.
BTW, you need to remember that honking hot comment...
OK, we have an atmosphere that would make Venus proud and hey, humans might actually grow accustomed to sucking it in. It'll be a bit too much like living in your 7th grade gym locker room... but we're an adaptable species.
Now... here's a guess that will likely send the far more science-oriented among us screaming into the night... right after they found me in a dark alley and beat the crap out of me. But...
We need a lot of "light" water vapor. That suggests bonding it to something that will help it float.
H3O2 is more dense than water, but it has a lower specific gravity by volume, which suggests it might "float" in the atmosphere as vapor more easily than H2O. It's also slick (low coefficient of friction), which would give a large amount of it a somewhat glassene appearance and it would feel/be slippery (good for the fish!).
Now, let's mix that with just a bit of Ammonia. NOT A LOT! Just enough to lower the density a bit.
Finally, let's mix in some alcohol! (YAY! Happy fish!) A quick Google search lists ethanol as the preferred molecule. Based on the fact that my more libatious friends in high school actually lived through high school, I'm going to go out on a limb and guess humanity could withstand 25% ethanol in the water-vapor-brew.
And something altogether magical that keeps those three elements bonded together without weighing them down like iron. I'm going to utterly ignore that, too. Thbppttt!
OK, I'm guessing again, but let's say 74% H3O2, 25% ethanol, and 1% ammonia. (And let's hope the beating I get doesn't break any bones.)
So, what I sincerely believe (that's a really strong word, here. Maybe "wish" would be better!) is that we have a breathable atmosphere with a lucious, thick water vapor layer above it that just might be thick enough (thanks to the heat!) for a fish (well... a flying fish, anyway) to live in. The critters that evolve to love this layer will fly-swim in it, but are very unlikely to ever exit it as their flying ability won't lift them in the thin upper atmosphere and their swim ability won't save them when they plummet to the ground in the lower atmosphere. Hydrogen sacks would help tremendously. And my guess is that from space the planet would look like a cloud-covered mirror. If you live on the surface, don't expect to see the sun anytime soon.
And it will be HOT! HOT HOT HOT! So you might not end up with an hospitable planet.... That would be a weakness in the storyline, overcoming what might be debilitating heat... But just maybe.... The critters of such a planet would be COOL! (no actual pun intended. ... well, maybe a little one.)
My muse behind this was the atmosphere of Titan and the layered atmospheres of Jupiter and Saturn. Which are nothing at all like I described.