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I would use a combination of sonar, radar and visual technique. Sonar only is a neat trick, but all manner of variations are possible.
I don't know how much sense it will make to you right now, but what I've done is first, accurately plot the target's course and speed with radar. Set yourself up for a Dick O'Kane attack at the limit of visibility, hopefully between 500 and 1000 yards. At this point the only piece of information you care about is bearing to the target.
Shoot when the radar or sonar bearing is correct for your lead angle. You can even shoot using passive sonar only! Make it a spread then because passive sonar has a bit of lag sometimes. He might actually be ahead of the sonar line. The line is already corrected for MOT (middle of target).
Of course if you see him, you can shoot visually on the correct lead angle and tag him every time.