Intersecting a plane with another plane, creating a cut (Boolean/knife project doesn't work) I'm working on this project where I want to connect a floor to a wall. My understanding of Blender is still pretty basic so my workflow has a lot of hiccups. What I'm trying to create is a canal with its underwater climate.

That said, this is what I did:


Extrude a cube in a hallway 
Delete the top plane
Separate the bottom    (floor) plane from the wall
Adding an ocean modifier to make it look    like an underwater
ground.
Dragged the sides up slightly with some    sculpting


The walls are pretty basic right now, but I actually want to add a brick wall displacement texture to give it depth.  

I decided to skip that step because I'm already stuck at my current problem. That problem is attaching the walls back to the floor by making them intersect.

I'm essentially looking for a way to create a ''slit'' in the wall, by making the floor intersect with it as seen below.



Boolean seems to be of no help and I can't find any information.
I tried to dumb down the problem by making two simple planes intersect like so:


But even with a simple setup like that, I couldn't get it to work.
Any tips on my workflow are appreciated.

The only thing I can think of to do is to never separate the bottom plane from the walls and to modify the floor myself by sculpting. In that case, I will give the walls their own texture and use a displacement modifier to give it the depth.

TLDR: I'm trying to cut a plane with another plane (two separate objects) and Boolean or knife project is not working the way I want it to.
A bit of depth seems to help. In the following image the target of the modifier has some depth (using Boolean Difference) and it seems to work nicely.