I'm trying to create some low poly water, and for whatever reason the displacement modifier is not functioning. I have about 100 subdivisions on the object and when I click "displacement", it works until I click "new texture", where instead of displacing the plane it just moves it extremely low.
The "new texture" is still on the defaults, which just aren't very interesting, yet. It just has too little noise to do anything on the displacement.
Click on the button all the way to the right of the texture's name in the displacement modifier. This will take you to the settings for this texture. You'll need to reduce the scale of the texture so that the portion mapped to the plane has some variation, instead of being mostly the same color.
EDIT: Or Zak might be right, there might just not be an actual texture associated with it, yet.