Underwater Sound Problem

Hey guys,

I made a script and the visuals work, however when i play the game the sound only plays once im above the water instead of under it. How can i fix this?

using UnityEngine;
using System.Collections;

public class Underwatersrc : MonoBehaviour {
	public AudioClip Underwatersound;

	void Update() {
		if(Camera.main.transform.position.y < 750){
		RenderSettings.fogMode = FogMode.Exponential;
		RenderSettings.fog = true;
			RenderSettings.fogDensity = 0.085f;
			RenderSettings.fogColor = new Color (0.22f, 0.65f, 0.77f, 0.5f);
		    audio.clip = Underwatersound;
		else {
				RenderSettings.fogMode = FogMode.Linear;
		RenderSettings.fog = true;
			RenderSettings.fogDensity = 0.85f;
			RenderSettings.fogColor = Color.white;

what its happening is this, when you are underwater, every time it updates, the underwater clip, starts playing, over and over again
you can check for (AudioSource)audio.isPlaying, to only make it play when its not

if(audio.isPlaying == false)

Thank you sir