Glad to hear it, yeah this game does kick ass. I'm pretty new to it too but I've logged quite a few hours in the last few weeks
Yeah that hydrophone will help you find targets up to 20km, much farther than your watch crew especially in fog, but it helps if you have the volume on it turned all the way up. I don't know if you've noticed it, but it's that black knob near the wheel. There's no obvious way to turn it up or down, you just have to click it and drag it around until the sound is loudest. Only thing is, you won't notice whether the volume is actually going up or down unless you are actually pointed at a target with it. So, rather than wait till I'm searching for a merchant to play with the volume, I run my electric engines and then turn the hydrophone at 180 so I can hear my own screws, then I adjust the volume to the max. Then when I'm searching for targets later on I'llk now that the volume is all the way up. That'll make sure you don't miss any fat targets just because the volume wasn't all the way up