Interesting answers thanks
But I was not much concerned about depth in regards of torpedo usage, but rather to gain informations like "the contact is at missile launch depth" or "the contact is decreasing his depth".
In the game, this information could (maybe) be of some use, for example it could raise the doubt that it's going to perform an asrocs launch, or more interesting, that he's going to engage some Land-Target. In some missions that could force me to engage the contact immediately instead of waiting for a better situation :hmm:
Maybe I could even tell if he's trying to hide ecc ecc...