Modify the scale of an another transform

I have to modyfy the scale of a sprite from my object controller, the sprite hasn’t a script attached to it. The controller has three scripts in it, one of theese script has:

public GameObject WaterSignal;
public float WaterLevel;
public float MaxWaterLevel;
public float PercentWater;
[...]


void Update () {
   Check ();
   PercentWater = (WaterLevel / MaxWaterLevel)*100;
   WaterSignal.GetComponent<transform>() //here i don't know how to proceed
[...]

Take a look here:

http://docs.unity3d.com/ScriptReference/Transform-localScale.html

  WaterSignal.transform.localScale += new Vector3(1.5f, 0f, 0f); //scale the x by 1.5