Water physics / floating

So this question has probably been asked a million times already, but all the posts I've found about this are either 10 years old or have no answers.
It's pretty simple, I want to be able to float in water, just the basics without diving or anything too complicated yet. What is the best way to do this?
I've tried using:

 void OnTriggerEnter()
 {
     CharacterController controller = player.GetComponent<CharacterController>();
 
     controller.Move(Vector3.up * 10f);
 }

But that is obviously not smooth at all, and it's really glitchy.
I read somewhere on an old post that someone used Mathf.moveTowards(), and you could probably use Lerp as well.
Or do I have to switch to rigidbody physics in water? That's fairly easy, but it doesn't seem like it's necessary.

So what is the best way to make smooth water physics? Thanks!