Floating in midair with a Rigidbody2D(Not gravityScale = 0)

Floating.cs

using UnityEngine;

public class Floating : MonoBehaviour
{
    protected Rigidbody2D rbody;

    void Start()
    {
        this.rbody = GetComponent<Rigidbody2D>();
        this.rbody.mass         = 20;
        this.rbody.gravityScale = 1f;
    }

    void FixedUpdate()
    {
        // rectify round-off error
        float gravityForce = Mathf.Ceil(this.rbody.mass * this.rbody.gravityScale * -Physics2D.gravity.y * 1000000f) / 1000000f;
        this.rbody.AddForce(Vector2.up * gravityForce);
    }
}