Yes for first person crouching as Rares15 has figured out. You can create from the first person character and add an empty game object. Then put the character camera into the empty game object and apply this script to the empty game object. I have made the numbers a public float so you can play around with the standing height and the crouched height.
using UnityEngine;
public class Crouch : MonoBehaviour
{
public float playerCrouched = -0.75f;
public float playerUncrouched = 0f;
private void Update()
{
if (Input.GetKeyDown(KeyCode.LeftControl))
{
transform.localPosition = new Vector3(0, playerCrouched, 0);
}
if(Input.GetKeyUp(KeyCode.LeftControl))
{
transform.localPosition = new Vector3(0, playerUncrouched, 0);
}
}
}