globalFlock.cs

using UnityEngine;
using System.Collections;

public class globalFlock : MonoBehaviour {

    public GameObject fishPrefab;
    public GameObject gol;
    public static int tankSize = 5;

    static int numFish = 20;
    public static GameObject[] allFish = new GameObject[numFish];

    public static Vector3 goalPos = Vector3.zero;

    // Use this for initialization
    void Start ()
    {
        for(int i = 0; i < numFish; i++)
        {
            Vector3 pos = new Vector3(Random.Range(-tankSize,tankSize),
                                      Random.Range(-tankSize,tankSize),
                                      Random.Range(-tankSize,tankSize));
            GameObject g = (GameObject) Instantiate(fishPrefab);
            g.transform.SetParent (transform);
            g.transform.localPosition = pos;
            g.transform.rotation = Quaternion.identity;
            allFish [i] = g;
        }
    }

    // Update is called once per frame
    void Update ()
    {
        if(Random.Range(0,10000) < 50)
        {
            goalPos = new Vector3(Random.Range(-tankSize,tankSize),
                                  Random.Range(-tankSize,tankSize),
                                  Random.Range(-tankSize,tankSize));
            gol.transform.localPosition = goalPos;
        }
    }
}