Fall off map in Blender Geometry Node terrain generator

[Bitterman1021 (Redblob)]

Hello! I know this is blender and technically doesn’t belong here but I don’t have anywhere else to ask.
I was wondering how I can add a falloff map to my geometry node setup for my terrain generator.
I’ve tried many solutions and I just cannot for the life of me get it to work.
Here is my setup

Any help would be greatly appreciated

[Bitterman1021 (Redblob)]

I got a standard fall off to work, however, now I’m trying to figure out how to have the falloff dip down below zero to allow me to have a shore line so I can add a water plane

Here is my setup for the falloff

Any ideas?