Custom camera projection matrix of orthographic camera

I solved it by casting rays of the bottom of my screen twords the water and reconstructing the orthographic view after that:

 // This code snippet is attatched to the main camera
 // Create rays for bottom corners of the camera
 Ray bot_right_ray = Camera.main.ViewportPointToRay(new Vector3(1, 0, 0));
 Ray bot_left_ray = Camera.main.ViewportPointToRay(new Vector3(0, 0, 0));
         
 // Move camera after main camera
 planar_reflection_manager.ConstructMatrix4X4Ortho(bot_right_ray, bot_left_ray, 2f * m_camera.orthographicSize, transform.rotation * Quaternion.Euler(-60f, 0f, 0f));
 planar_reflection_manager.SetCameraNearClippingPlane();

planar_reflection_manager script (attatched to the reflection camera):

 public void SetCameraNearClippingPlane()
 {
     Vector4 clipPlaneWorldSpace = new Vector4(0f, 1f, 0f, -Water.water_level);
     Vector4 clipPlaneCameraSpace = Matrix4x4.Transpose(Matrix4x4.Inverse(reflection_camera.worldToCameraMatrix)) * clipPlaneWorldSpace;
     reflection_camera.projectionMatrix = Camera.main.CalculateObliqueMatrix(clipPlaneCameraSpace);
 }
   
 public void ConstructMatrix4X4Ortho(Ray bot_right_ray, Ray bot_left_ray, float camera_orthographic_height, Quaternion camera_rotation)
 {
     // Construct plane representing the water level
     Plane plane = new Plane(Vector3.up, -Water.water_level);
 
     // Assign floats of ray distance for bottom corners
     float bot_right_distance;
     float bot_left_distance;
 
     // Raycast to plain
     plane.Raycast(bot_right_ray, out bot_right_distance);
     plane.Raycast(bot_left_ray, out bot_left_distance);
 
     // Get each position of all four camera corners where they hit the water plain
     Vector3 top_right_position = bot_right_ray.GetPoint(bot_right_distance);
     Vector3 top_left_position = bot_left_ray.GetPoint(bot_left_distance);
 
     // Get sidebar of new camera
     Vector3 camera_sidebar_direction = camera_rotation * Vector3.down;
     Vector3 camera_sidebar = camera_sidebar_direction * camera_orthographic_height;
 
     // Create the vectors representing bottom corners of our new worldToCameraMatrix.
     Vector3 bot_right_position = top_right_position + camera_sidebar;
     Vector3 bot_left_position = top_left_position + camera_sidebar;

     // Assign that point to the camera position and rotate camera
     // Get middle point of our four points
     Vector3 middle = (top_right_position + top_left_position + bot_right_position + bot_left_position) * 0.25f;
 
     reflection_camera.transform.position = middle;
     reflection_camera.transform.rotation = camera_rotation;
 
     //Matrix4x4 world_to_camera_matrix = Matrix4x4.Ortho(-10, 10, -10, 10, 0, 10); // You could probably create an ortho matrix from theese cords but i do not now how
 }

The code should be self explanatory with the comments but ill also leave this OnDrawGizmos code snippet with its representing image.

 private void OnDrawGizmos()
     {
         // Construct plane representing the water level
         Plane plane = new Plane(Vector3.up, -Water.water_level);
 
         // Create rays for bottom corners of the camera
         Ray bot_right_ray = Camera.main.ViewportPointToRay(new Vector3(1, 0, 0));
         Ray bot_left_ray = Camera.main.ViewportPointToRay(new Vector3(0, 0, 0));
 
         // Assign floats of ray distance for bottom corners
         float bot_right_distance;
         float bot_left_distance;
 
         // Raycast to plain
         plane.Raycast(bot_right_ray, out bot_right_distance);
         plane.Raycast(bot_left_ray, out bot_left_distance);
 
         // Get each position of all four camera corners where they hit the water plain
         Vector3 top_right_position = bot_right_ray.GetPoint(bot_right_distance);
         Vector3 top_left_position = bot_left_ray.GetPoint(bot_left_distance);
 
         // Draw red raycasts twords those points
         Gizmos.color = Color.red;
         Gizmos.DrawRay(bot_right_ray.origin, bot_right_ray.direction * bot_right_distance);
         Gizmos.DrawRay(bot_left_ray.origin, bot_left_ray.direction * bot_left_distance);
 
         // Draw a yellow sphere at the hit location
         Gizmos.color = Color.yellow;
         Gizmos.DrawSphere(top_right_position, 1);
         Gizmos.DrawSphere(top_left_position, 1);
 
         // Get height of orthographic camera
         float camera_height = 2f * m_camera.orthographicSize;
 
         // Get sidebar of new camera
         Vector3 camera_sidebar_direction = transform.rotation * Quaternion.Euler(-60f, 0f, 0f) * Vector3.down;
         Vector3 camera_sidebar = camera_sidebar_direction * camera_height;
 
         // Continue drawing magenta raycast that represent the bottom screen edges
         Gizmos.color = Color.magenta;
         Gizmos.DrawRay(top_right_position, camera_sidebar);
         Gizmos.DrawRay(top_left_position, camera_sidebar);
 
         // Create the vectors representing each corner of our new worldToCameraMatrix.
         Vector3 bot_right_position = top_right_position + camera_sidebar;
         Vector3 bot_left_position = top_left_position + camera_sidebar;
 
         // Draw 
         Gizmos.color = Color.green;
         Gizmos.DrawSphere(bot_right_position, 1);
         Gizmos.DrawSphere(bot_left_position, 1);
 
         // Yellow points are now representing the top right and top left corners of our new camera whilst the green points represent bottom right and bottom left corners.
     }