Sonar Tracking

[xptical]

I am bout 3500 meters from a ship. It is closing. I know it's closing because my sonar man says so. I know the range because I used the periscope. I wanted to submerge and follow the target on sonar only. I have the bearing line on my nav map. I click over to sonar and click the "range to target" button and get a report that I have no target.

How should I properly discpline a sonar man that can't figure out that if there is only one track, that's probably the one I want?

I was thinking of submerging to 50 meters and let him see if he can reach the surface before he drowns.

After that, how do I tell his replacement which target I want range to?