Modifing Standard Assets FPC to swim

I have found many similar questions to this one, most of them have no answers or just theoretical guidelines.

I used the First Person Controller (Using Character Controller not the rigid body version) prefab provided in Unity's Standard Assets Pack. I have not modified it in anyway as of yet, except for adding an empty child with a sphere collier set to isTrigger. This object was moved up on the y-axis to represent the head. I attached a script to the head that checks if I entered and exited the water. This all works, now I just need the "physics" of swimming, if I was using a rigid body I could just toggle the gravity off and on when I enter and exit the water. I'm not really too concerned with swimming backwards or sideways. Just forward in the way the player is facing.

I have read that using CharaterController.Move(); instead of CharaterController.SimpleMove(); should fix the problem. However that does not seem to be a quick modification as the script provided by unity seems to rely on the CollisionFlags returned by CharaterController.Move();

So before I scrutinize every line of code, of rewrite my own controller, I thought someone might have a quick and sensible solution? I don't need a super complex swimming system, just basically need to turn the gravity off and on.

Here's my trigger code if you want to reference it:

 using UnityEngine;
 using System.Collections;
 using UnityStandardAssets.ImageEffects;
 
 public class SwimController : MonoBehaviour
 {
     public BlurOptimized blur;
     public GameObject colorOverlay;
 
     private bool isSwimming;
 
     public void OnTriggerEnter(Collider other)
     {
         if (other.tag == "Water")
         {
             // player entered water
             blur.enabled = true;
             colorOverlay.SetActive(true);
         }
     }
 
     public void OnTriggerExit(Collider other)
     {
         if (other.tag == "Water")
         {
             // player exited water
             blur.enabled = false;
             colorOverlay.SetActive(false);
         }
     }
 }