Floating Water Idea

So my mind is caught on this idea now. What if liquids were lighter than gasses? Like I know it's a physical impossibility, but it's an interesting premise. Because all the air would be where the oceans are, and the oceans would float on top. The water would make the air covered earth we live on darker, pitch black in places. However industry would eventually solve that with electricity. Also it would be harder to get water to survive, we would have to drill for trapped water pockets under ground like we now drill for oil. Also what would transportation be like? Cars and such would still exist, but I don't think planes would. I think we would just have elevators up to water level and have subs. In fact, we may have semi bouyant buildings floating above entire metropolises below. And what would space travel be? What would astrology be like? Could we see stars, or would schools of shining fish be equivalent? Imagine seeing a whale float above you in the moonlight. Also, how different would the ocean be without rooted in the ground plants? Would plants be rooted to tall mountains? Or would there be places where the elevation is high enough to where there's no air and it's surrounded by water? Or bottom feeders? What would happen to food that fell deeper into the sea? Would it rest on the waters edge at the bottom, or would it slip through and fall through the air below?

Also, I know we as humans are mostly water. I'm presuming that we land life forms would be heavy enough to not float above the air due to the light water in our body, just because of other things in us. Dunno. It just interests me.