Hi

 

"Drain" is a block with the intention of allowing entities to walk over it and interact with it physically while letting fluids to pass through it. Water Logging allows blocks to hold a water source, but it still blocks incoming fluids flowing towards it. And a waterlogged block only allows for water to fall down it if the hitbox is "open" in that direction.

 

My Drain Block:

 

Example of how water is blocked by the hitbox:

 

And how it should behave:

 

Then there is the water pathfinding the lowest point it can move to.

How it is right now:

 

How it should be like (behaving as if there was a ledge instead of a block):

 

And a picture without the water:

1 hour ago, Simon_kungen said:

but it still blocks incoming fluids flowing towards it.

This is because the "waterlogged" system isn't finished.

1 hour ago, Draco18s said:

This is because the "waterlogged" system isn't finished.

Huh... I thought Mojang was done with it as I haven't seen any mentions of it in any future updates.

Try any vanilla block and flowing water. None of them function with it either.