2D GameObject Array to 2D List

I have a 2D GameObject array, and I want to convert it into a 2D GameObject List. Using .ToList() gives a error. Is there a way to use something like .ToList() to convert this array, or will I have to craft the list from the array myself?

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class Test : MonoBehaviour {

	private GameObject[][] array2D;
	private List<List<GameObject>> list2D = new List<List<GameObject>>();

	void Update () {
		array2D = list2D.ToList ();
	}
}

The error the console gives is:

Cannot implicitly convert type `System.Collections.Generic.List<UnityEngine.GameObject[]>' to `System.Collections.Generic.List<System.Collections.Generic.List<UnityEngine.GameObject>>'

You are dealing with a two dimensional array and a one dimensional, resizable array (essentially, that is what a list is). I suppose you can create a custom List class to handle such a conversion but as @maccabbe said, this is not possible.