How do you even know it's water?
How do you even know that gravity is working correctly?
Maybe you're really doing a handstand?
Correct. You are not just dreaming, you are projecting yourself into different dimensions, and therefore anything could be changed.
You are wondering how this all started.
Well, it didn't. You went into a coma when you were born..Although this is what you've thought of this whole time. You have no recollection of anything before the first dimensional shift.
You don't even remember that correctly. You've spent what you recall almost six centuries trying to figure out how to get out of your coma and back to life.