Need some help optimizing this

I found a tutorial on how to make a cool water effect in as3 using bitmap data and a displacemnt filter. It works great but it is very heavy on the computer.

here is my code

var bmd:BitmapData = new BitmapData(700, 398);
var dmf:DisplacementMapFilter = new DisplacementMapFilter(bmd, new Point(0,0), 1, 2, 10, 30);
var p1:Point = new Point(0, 0);
var p2:Point = new Point(0, 0);
var perlinOffset:Array = [p1, p2];

addEventListener(Event.ENTER_FRAME, loop);

function loop(e:Event):void {
    perlinOffset[0].x += 0.8;
    perlinOffset[1].y += -0.6;
    bmd.perlinNoise(168, 5, 2, 4, true, true, 2, true, perlinOffset);

Here is a liink to the swf

Any one have any ideas on how to speed this up?