How to float a boat in a deformed mesh?

I have a script which deforms a mesh. This script also updates the mesh collider so that the waves will properly collide with things and shove them around. This part works super awesome great.

I've gone this route to attempt to add buoyancy and I think the 'fake' hovering object is good because you can definitely tell how close to the water the object is but I'm having trouble nailing force modes and when to apply the force.

 #pragma strict
 
 var raycaster : GameObject;
 
 function Start()
 {
         //create the primitive
         raycaster = GameObject.CreatePrimitive(PrimitiveType.Sphere);
         
         //turn off the renderer on it
         raycaster.gameObject.renderer.enabled = false;
         
         //parent the primitive
         raycaster.gameObject.transform.parent = gameObject.transform;
         
         //place the primitive
         raycaster.transform.position = Vector3(transform.position.x, transform.position.y+100, transform.position.z);
             
         //name the primitive
         raycaster.name = "raycaster";
 }
 
 
 function Update () 
 {
     var hitall : RaycastHit[] = Physics.RaycastAll(raycaster.transform.position, -Vector3.up, 1000) ;
     print(hitall[0].collider.gameObject.name);
     print(hitall[0].distance);   
     
     if(hitall[0].collider.gameObject.name == "Water")
     {
         if(hitall[0].distance < 100)
         {
             print("adding force");
             rigidbody.AddForce( Vector3(0,100-hitall[0].distance,0), ForceMode.Force);
         }
         else
         {
             rigidbody.AddForce( Vector3(0,-100,0), ForceMode.Force);
         }    
     }    
 }