OldBlueWater/BlueWater/Assets/02.Scripts/WaterAndShip/Gerstner wave/Floater.cs

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

public class Floater : MonoBehaviour
{
    public GerstnerWave waveGenerator;
    public float boatOffset = 0.0f;  // new variable
    private Rigidbody rb;

    private void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    public void Update()
    {
        float waveNumber = 2.0f * Mathf.PI / waveGenerator.waveLength;
        float phaseConstant = waveGenerator.speed * waveNumber;
        Vector3 position = rb.position;
        float dotProduct = Vector2.Dot(new Vector2(position.x, position.z), waveGenerator.direction);
        float wavePhase = waveNumber * dotProduct + phaseConstant * Time.time;

        // Calculate the new height
        float newY = waveGenerator.amplitude * Mathf.Sin(wavePhase) + boatOffset;  // added offset here
        position.y = newY;

        rb.MovePosition(position);

        // get wave's normal
        Mesh mesh = waveGenerator.GetComponent<MeshFilter>().mesh;
        Vector3 normal = mesh.normals[0];

        Quaternion targetRotation = Quaternion.FromToRotation(transform.up, normal) * transform.rotation;
        rb.MoveRotation(Quaternion.Slerp(transform.rotation, targetRotation, Time.deltaTime * waveGenerator.speed));
    }
}