What is the best way to add movement to a bouyancy and physics script?

Question

I am writing a endless runner using a water-based system, and found a buoyancy script named "Floater" that works very well. However, now I'd like to add rotation and forward movement, but I can't find a way to add to the script without disrupting the force applied.

 using UnityEngine;
 using System.Collections;
 
 public class Floater : MonoBehaviour {
     public float waterLevel, floatHeight;
     public Vector3 buoyancyCentreOffset;
     public float bounceDamp;
     
     private float yaw = 0;
 
     void FixedUpdate () {
         yaw = Input.GetAxis("Horizontal") * (Time.deltaTime * 30f);
         Vector3 addRot = Vector3.zero;
         
         addRot.y = yaw;
         
         transform.Rotate(addRot);
         
         Vector3 actionPoint = transform.position + transform.TransformDirection(buoyancyCentreOffset);
         
         float forceFactor = 1f - ((actionPoint.y - waterLevel) / floatHeight);
         
         if (forceFactor > 0f) {
             Vector3 uplift = -Physics.gravity * (forceFactor - rigidbody.velocity.y * bounceDamp);
             rigidbody.AddForceAtPosition(uplift, actionPoint);
             Debug.Log (uplift);
         }
         
         
     }
 }

Answer 1

You can include an AddForce in order to make it move in the desired direction - in this case, the object's forward direction (you could instead use a world direction, like Vector3.forward).

 ...
 public float bounceDamp;
 public float force = 10.0f; // this is the move force
 
 private float yaw = 0;
 
 void FixedUpdate () {
    yaw = Input.GetAxis("Horizontal") * (Time.deltaTime * 30f);
    Vector3 addRot = Vector3.zero;
    addRot.y = yaw;
    transform.Rotate(addRot);
    Vector3 actionPoint = transform.position + transform.TransformDirection(buoyancyCentreOffset);
    float forceFactor = 1f - ((actionPoint.y - waterLevel) / floatHeight);
    if (forceFactor > 0f) {
      Vector3 uplift = -Physics.gravity * (forceFactor - rigidbody.velocity.y * bounceDamp);
      rigidbody.AddForceAtPosition(uplift, actionPoint);
      Debug.Log (uplift);
    }
    // add the movement force
    float fwd = Input.GetAxis("Vertical") * Time.deltaTime * force;
    rigidbody.AddForceAtPosition(fwd * transform.forward, actionPoint);
 }

You could as well implement the rotation via AddTorque: the result would be more realistic (although many times we don't want it too realistic) - example:

 void FixedUpdate () {
    yaw = -Input.GetAxis("Horizontal") * (Time.deltaTime * 5f);
    rigidbody.AddTorque(new Vector3(0, yaw, 0)
    Vector3 actionPoint = transform.position + transform.TransformDirection(buoyancyCentreOffset);
    ...

NOTE: Increase the Drag and AngularDrag to make the movement and rotation cease gradually when the force/torque are removed.

What is the best way to add movement to a bouyancy and physics script?

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