Creating Water

I figured out how to make water using

; ---------------------------------------------------------------
; Water...
; ---------------------------------------------------------------

water = CreatePlane ()
h20 = LoadTexture ("gfx/water.bmp")
ScaleTexture h20, 200, 200
EntityTexture water, h20
EntityAlpha water, 0.4
PositionEntity water, 0, .15, 0
EntityShininess water, 1

; ---------------------------------------------------------------
; Collision Information...
; ---------------------------------------------------------------

Const ENTITY_BOX = 1
Const ENTITY_WATER = 2

Collisions ENTITY_BOX,ENTITY_WATER,2,2

But what I want to know is how do you make water move
like water does.