[Sailor Steve]

You say you dive deep and change course. Anything else? Silent running?

Go deep, go slow, go silent. As Nisgeis said, turn your tail to the attackers for a smaller 'ping' profile. You should hear the destroyer's propellors when he gets close. If they sound slow he likely doesn't have you, whether you hear pings or not. If you hear him pick up speed that means he is accelerating so he doesn't blow his own stern off. This also means he can't hear you anymore, because sonar doesn't work at higher speeds and because it only points down so far, and when he drops his charges he's dropping 'blind'.

In the stock game this doesn't work. He hears you no matter what, and his bombs almost never miss. In both RFB and TMO this works as it should. So...

When you hear him pick up speed, go to flank yourself, go to right or left full rudder (if he's coming in from one side, turn toward him, as this helps to throw off his aim), and go down another fifty feet or more. As soon as the charges stop falling go slow again and creep back up to 200 feet or so. None of this is a guarantee, but when he's looking for you low and slow makes you harder to find, and when he's attacking you fast and squirmy makes you harder to hit.