Freezing GameObject in place using collider trigger?

I have a script where I want to capture a fish but while having it wait a certain amount of seconds the prefab keeps moving using another script called way points. how can I stop the prefab in place? I tried
fishdist = 0; in Update but that doesn't seem to work. Thank you so much :'(

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

public class Casting : MonoBehaviour {

 public ParticleSystem Splash;
 public float offsetSplash;

 public GameObject Float;
 public GameObject Item;
 public GameObject Enemy;


 public Transform target;
 public Transform targetItem;
 //public Transform targetEnemy;

 public int scoreValue = 10;
 int waterMask;

 public float maxCastDist = 1000f;
 public float fishDist = 1f;
 //public float itemDist = 1f;
 //public float enemyDist = 1f;

 public bool hitObject;

 public string achievmentName;


 void Awake ()
 {
     
     waterMask = LayerMask.GetMask ("Water"); // will only cast in water
 }



 void Update ()
 {
     //if (Input.GetMouseButtonDown (0)) {
     if (EventSystem.current.IsPointerOverGameObject ()) {
         return;

     } else {

         if (Input.GetMouseButtonDown (0)) {

             RaycastHit hit;


             Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);

             Vector3 splashOffset = Input.mousePosition;

             splashOffset.y = Input.mousePosition.y + offsetSplash;

             Ray offset = Camera.main.ScreenPointToRay (splashOffset);

             if (Physics.Raycast (offset, out hit, maxCastDist, waterMask)) {
                 if (hit.collider != null) {
                     if (Splash != null) {
                         ParticleSystem splash = Instantiate (Splash, hit.point, Quaternion.identity) as ParticleSystem;
                         splash.Play ();
                     }
                 }
             }


             if (Physics.Raycast (ray, out hit, maxCastDist, waterMask))
             if (hit.collider != null) {

                 float dist = Vector3.Distance (hit.point, target.position);
                 Debug.Log (dist);

                 Instantiate (Float, hit.point, Quaternion.identity);
                 if (dist < fishDist) {

                     // stop fish in place 
                     //fishdist = 0;
                     StartCoroutine (fishWaiter ()); // delay random when fish will be "retrieved"
                 } 

             }
         }
     }
 }

 


 IEnumerator fishWaiter ()
 {

     int waitFishtime = Random.Range (1, 10);
     Debug.Log ("Timer Started");
     yield return new WaitForSeconds (waitFishtime);
     print ("I waited" + waitFishtime + "Sec");

     Destroy (GameObject.FindWithTag ("Fish"));

 
     print ("You Caught The Fish!");
     ScoreManager.score += scoreValue;
     AchievementManager.Instance.EarnAchievment (achievmentName);
 }

}