For a long time now I suspected a bug concerning Submarine Hydrophone Consumable, I would often have Hydrophone running (for well over 6seconds), while submerged, detecting nothing, then 5s later I would surface and bump into a ship 3km away from me, that my 7km or 8km Hydrophone should have detected. I started copying replays demonstrating the problem to study the bug and prepare a bug report. Now that Submarines are allowed in Training room battles, I tried studying the bug. The bug/problem turned out to be very simple - Submarine Hydrophone Consumable WORKS ONLY when there is line of sight between the Submarine (detection point), if there is any land between the Submarine (detection point) and the enemy ship Submarine Hydrophone Consumable does not detect/provide updates on that enemy ship. Judging from how Hydroacoustic Search, Radar, 2km Proximity spotting work (all those methods work through islands and ignore land, dont need line of sight) Submarine Hydrophone should also work through land, that is an obvious assumption every single player will make. I think the problem is a bug caused by a coding mistake. If this is an intended game feature, players should have been informed about it many many times already, and yet no Article or official Video mentioned it, also the Tooltip for Submarine Hydrophone Consumable absolutely should have mentioned it, if it is indeed intended.
Short version : Submarine Hydrophone does not work through land BUG or FEATURE ? Please clarify.