Underwater effect error

You know… I was having some problems with making an underwater effect recently, so i chose to just copy and paste a script that i have found in the SUPPOSEDLY Unity’s official Wikia.
(Also, you guys should get that thing offline, the last time it’s scripts were updated was a long time ago).

I’ve tried to update, i tried to change some things, but i still get two errors:

This is the script:

using UnityEngine;
using System.Collections;

public class UnderWater : MonoBehaviour
{

    //This script enables underwater effects. Attach to main camera.

    //Define variable
    public int underwaterLevel = 7;

    //The scene's default fog settings
    private bool defaultFog = RenderSettings.fog;
    private Color defaultFogColor = RenderSettings.fogColor;
    private float defaultFogDensity = RenderSettings.fogDensity;
    private Material defaultSkybox = RenderSettings.skybox;
    private Material noSkybox;

    void Start()
    {
        //Set the background color
        GetComponent<Camera>().backgroundColor = new Color(0, 0.4f, 0.7f, 1);

    }

    void Update()
    {
        if (transform.position.y < underwaterLevel)
        {
            RenderSettings.fogColor = defaultFogColor;
            RenderSettings.fog = true;
            RenderSettings.fogColor = new Color(0, 0.4f, 0.7f, 0.6f);
            RenderSettings.fogDensity = 0.04f;
            RenderSettings.skybox = noSkybox;
        }
        else
        {
            RenderSettings.fog = defaultFog;
            
            RenderSettings.fogDensity = defaultFogDensity;
            RenderSettings.skybox = defaultSkybox;
        }
    }
}

Can anyone help me to identify and fix those bugs? Also, if one of you happen to be a WebMaster of the website, you could also edit the page. Here’s the original outdated link:
Unity Wikia

Ah, and before someone ask “Oh, it is so simple, why didn’t you follow the instructions?” Because i am so tired that i can’t even think right AND because these lines actually doesn’t exist… You know… seriously.

Have you tried moving the initialization stuff inside a function rather than having it with the variable declaration?

//The scene's default fog settings
private bool defaultFog;
private Color defaultFogColor;
private float defaultFogDensity;
private Material defaultSkybox;
private Material noSkybox;

void Awake ()
{
    defaultFog = RenderSettings.fog;
    defaultFogColor = RenderSettings.fogColor;
    defaultFogDensity = RenderSettings.fogDensity;
    defaultSkybox = RenderSettings.skybox;
}