Unity Boat Script by MTIPUL

 /**********************************************************************\
    1. Create a "Water" layer, and a water plane with collision
    2. Create your boat prefab
        2A. Add a rigidbody. Here are my settings:
            mass = 1500
            drag = 1
            angular drag = 0.3
            use gravity = true

        2B. Add this script. Defaults should work w/rigidbody settings
        2C. Create 4 contact points, these will contact the water
            plane and apply upward force. Assign them to contactPoints
            array.
    3. Improve the script
        3A. Ex: You can make the noise based on a wind direction.
        3B. Cache things you'll need later, like the rigidbody
 \**********************************************************************/
using UnityEngine;

public class ShipController : MonoBehaviour
{
    public bool isPlayerControlled = true;
    public float forwardForce = 150;
    public float turnForce = 20;

    public Transform[] contactPoints;
    public float contactPointDistance = 2f;
    public float contactFloatForce = 4f;
    public Vector3 centerOfMassOffset = Vector3.zero;
    public float waveNoiseStrength = 0.95f;
    public float waveNoiseFrequency = 0.24f;
    public float waveNoiseScale = 0.24f;

    void Update ()
    {
        if (isPlayerControlled)
        {
            // oh god please do a better job than me, like moving this to FixedUpdate
            if (Input.GetKey(KeyCode.UpArrow))
            {
                Vector3 forwardForce = transform.forward;
                forwardForce.y = 0;
                forwardForce.Normalize();

                GetComponent<Rigidbody>().AddForce(forwardForce * this.forwardForce * Time.deltaTime, ForceMode.Acceleration);
            }
            if (Input.GetKey(KeyCode.LeftArrow))
            {
                GetComponent<Rigidbody>().AddRelativeTorque(new Vector3(0, -turnForce * Time.deltaTime, 0), ForceMode.Acceleration);
            }
            if (Input.GetKey(KeyCode.RightArrow))
            {
                GetComponent<Rigidbody>().AddRelativeTorque(new Vector3(0, turnForce * Time.deltaTime, 0), ForceMode.Acceleration);
            }
        }
    }

    private void FixedUpdate()
    {
        GetComponent<Rigidbody>().centerOfMass = centerOfMassOffset;

        for (int i = 0; i < contactPoints.Length; i++)
        {
            ApplyForceToContactPoint(contactPoints[i].position, contactFloatForce, contactPointDistance);
        }
    }

    void ApplyForceToContactPoint(Vector3 point, float forceScale, float distance)
    {
        RaycastHit hit;
        Vector3 force = Vector3.zero;
        if (point.y <= 0)
        {
            force = Vector3.up * forceScale;
        }
        else if (Physics.Raycast(new Ray(point, Vector3.up * -distance), out hit, distance, 1 << LayerMask.NameToLayer("Water")))
        {
            force = Vector3.up * (1f - (hit.distance / distance)) * forceScale;
        }

        float perlinOffsetX = Time.fixedTime * waveNoiseFrequency;
        Vector3 noiseForce = Vector3.up * Mathf.PerlinNoise((point.x * waveNoiseScale) + perlinOffsetX, (point.z * waveNoiseScale) + perlinOffsetX) * waveNoiseStrength;
        force += noiseForce;

        Debug.DrawLine(point, point + force, Color.yellow);
        Debug.DrawLine(point, point + noiseForce, Color.red);
        GetComponent<Rigidbody>().AddForceAtPosition(force, point, ForceMode.Acceleration);
    }

    private void OnDrawGizmos()
    {
        if (contactPoints != null)
        {
            for (int i = 0; i < contactPoints.Length; i++)
            {
                Gizmos.color = Color.white;
                Gizmos.DrawWireSphere(contactPoints[i].position, 0.2f);
                Gizmos.color = Color.blue;
                Gizmos.DrawLine(contactPoints[i].position, contactPoints[i].position - Vector3.up * contactPointDistance);
            }
        }

        Gizmos.DrawWireSphere(transform.position + centerOfMassOffset, 0.5f);
    }
}