Not always player surface ship can reach under layer. Sometimes layer is too deep and sometimes high speed prevents antenna to goo deeper (for example if player is escort of fast moving surf group)
Player can regulate TA depth via ownship speed or lenght of cable. For AI warship are discrete values for each TA types.
For example Type 23 Duke Frigate in RA database:
And ranges of depth (ft) / speed (kts) for TA:
