Use Collider like a radar...

Hey guys,

I am having major issues with the collider/collision concept it seems and I need a few clarifications.

The concept I am trying to make is like a submarine boat that uses sonar to detect other ships in the ocean. The boat itself has a collider (like a tube for its shape).

I added an empty GameObject, gave it a rigidbody component with zero mass and 'Is Kinematic' = true; and then added a sphere collider to the empty GameObject that can be adjusted to reach many hundreds of feet if necessary. I made this empty GameObject a child object of the boat.

Ideally, what I want to know is this:

1. If two sonar detection signals (sphereColliders) bump into each other, to detect a collision and report what transform the boat is (by using the parent information of course)

2. Do the OnCollisionEnter/Stay/Exit functions only work when the collision happens on the surface of the Collider? what happens if something is already inside the bounds of the collider? ( I ask this because I'm trying to report using Debug.Log(contact.otherCollider.name) and there is nothing to report even though my sample boats are all within range of each other).

I need some help with code that actually works because my usage of OnCollisionEnter and such is doing nothing at all in regards to collider detections.

 // Code //
 
 public SphereCollider sonarCollider;
 
 start(){sonarCollider.enabled = true;}
 
 void OnCollisionStay(Collision collision) {
 
         foreach (ContactPoint contact in collision.contacts) {
 
 Debug.Log(contact.thisCollider.name + " hit " + contact.otherCollider.name);
 
             print(contact.thisCollider.name + " hit " + contact.otherCollider.name);
 
             Debug.DrawRay(contact.point, contact.normal, Color.white);
         }
     }

..... and yet nothing is happening....