Quote: " but dont know what an fx file is or really how to use it."
Right click on the fx file, choose "open with" and then select notepad. An fx file is just a text file with special code in it. There might be built-in DBPro shaders to render water, but that would be more "3rd party" than using your own fx shader!
Quote: "mainly wanting refraction"
Yeah, you'll need a shader of some sort.
Well, an interesting experiment might to create a new camera, render the camera's image to a texture (using the matrix1utils plugins probably), and then texture the water plane with that image. It might not look the best though.
Quote: "please dont recomend a shader or plugin i refuse to use someone elses work i dont understand or cant properly modify"
I think this is a bad mindset, because EVERYTHING in DBPro uses someone else's work. Do you understand the graphics pipeline? How polygons are rendered/culled? What about how lines are drawn from the line function? There's a lot to learn and if you try to learn all of it while working on another thing, you'll probably get bored and give up. I know I have.