Unity crashes whenever i activate my script... ,I have a script that crashes whenever i activate it....

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class OilRigSpawnGen : MonoBehaviour {

 //public List<GameObject> units = new List<GameObject>();

 public GameObject waterTiles;

 void Update()
 {
     if (Input.GetKeyDown(KeyCode.G))
     {
         for (int x = 0; x < 3; x++)
         {
             for (int z = 0; z < 3; z++)
             {

                 this.gameObject.transform.position = new Vector3(gameObject.transform.position.x,0, gameObject.transform.position.z);
                 GameObject tileClone = Instantiate(waterTiles.gameObject, new Vector3(transform.position.x - (55 * x), 0, transform.position.z - (55 * z)), Quaternion.identity) as GameObject;

                 //units.Add(tileClone.gameObject);
             }
         }
     }
 }

}