WaterBody.cs

using UnityEngine;

//  --- How to setup ---
//
//   -Add box Collider on Water Body and set it as Trigger.
//   -Also Add "WaterBody" component On it (optionally you can change surface level property if needed)
//   -Give water object Tag as "Water" (or you can change "waterVolumeTag" property accordingly)
//   -Add "Buoyancy" component on a Rigidbody Object that you want to float on WaterBody.
//
//
//
//  --- What this Dose ---
//
//   -Rigidbody with "Buoyency" Component floats on "Water" Tagged body.
//   -Check if Rigidbody is inside X - Z bound of Water body and gives force on Y Upwards.
//   -Buoyant force (Upwards force) increases as rigibody dive deep underwater. (can be variable by depthPowerLimit property)
//
//
//
//  --- Limitations ---
//
//   -This is clearly NOT real world Physics, just simple Up force.
//   -No additional forces or drag or waves.
//   -As this component is limited to Y axis buoyancy, make sure your Y is up, however feel free to modify.
//   -Other collider types will work as long as water surface level stay flat, as this is designed on checking collider bounding box.
//   -Rigidbody never fall Asleep if inside water body.
//   -Don't stack water Bodies on top or duplicate on same location.

public class WaterBody : MonoBehaviour
{
    [SerializeField, Tooltip("Check this if you want to set Surface level of the water by yourself")]
    bool customSurfaceLevel = false;
    [SerializeField, Tooltip("Surface level of waterbody in Y axis")]
    float surfaceLevel = 0f;

    private Collider coll;


    private void Start()
    {
        coll = GetComponent<Collider>();
    }

    //Get Surface level of the water
    public float GetYBound()
    {
        if (!customSurfaceLevel) surfaceLevel = coll.bounds.max.y;
        return surfaceLevel;
    }
}