I have a multifloored building with a pool of water on a higher level. Unfortunately, all the floors under that pool are now underwater.

Is there a way to put a floor on water? or Limit it to only effect things in a multibound?

Non-scripting work arounds would be appreciated otherwise you might have to spell it out for me.

Thanks.

Nope. Water goes down for like 20000 units because it's not an actual bounding object. Water is just a plane with special properties that says 'if you're below this you're in water' instead of 'if you are in this volume of water, you're under water'. It's an engine thing, though it would be cool if they changed it for the next game. Then we could have suspended containers full of water and stuff like that.

The depth of the water attached to the planes is relative to its size, so you could try to utilize a series of smaller or scaled down water planes and see if you could fix it that way. I know that scaling up the size of a water plane increases the depth of the water.

This is true. You can see the depth of the water objects by viewing the collision geometry (F4). However, if you make an area with multiple water "blocks", the player will always take a breath when swimming from one block to another, even if you make them overlap.