Water distortion filter, implemented with Sparrow's "DisplacementMapFilter".

sparrow-distortion.m

- (void)addDistortionTo:(SPDisplayObject *)target
{
    float scale = Sparrow.contentScaleFactor;
    NSURL *url = scale == 1.0f ?
        [NSURL URLWithString:@"http://i.imgur.com/n95LSGb.jpg"] :
        [NSURL URLWithString:@"http://i.imgur.com/QRXLvws.jpg"];

    [SPTexture loadFromURL:url generateMipmaps:NO scale:scale
                onComplete:^(SPTexture *texture, NSError *outError)
    {
        float __block offset = 0;

        SPDisplacementMapFilter *filter = [[SPDisplacementMapFilter alloc] initWithMapTexture:texture];
        filter.componentX = SPColorChannelRed;
        filter.componentY = SPColorChannelRed;
        filter.scaleX = 40;
        filter.scaleY = 5;

        target.filter = filter;
        [target addEventListenerForType:SPEventTypeEnterFrame block:^(SPEnterFrameEvent *event)
         {
             if (offset > texture.height / 2.0f) offset -= texture.height / 2.0f;
             else offset += event.passedTime * 20.0f;

             filter.mapPoint.y = offset - texture.height / 2;
         }];
    }];
}