var explosionPrefab : Transform;
var damagedCar      : Transform;
function OnCollisionEnter(collision : Collision) {
     var contact : ContactPoint = collision.contacts[0];
     var rot : Quaternion = Quaternion.FromToRotation(Vector3.up, contact.normal);
     var pos : Vector3 = contact.point;
     if (collision.gameobject.tag == "water") {
         
          Instantiate(explosionPrefab, pos, rot);
          Instantiate(damagedCar, pos, rot);     
          // Destroy the projectile
          Destroy (gameObject);
     }
}