The triple guns are actually on the cruiser. Probably the best way to get the range for targets on land is to use "Land Mode" by pressing W on your keyboard. Then bring up the map with the ESC key, zoom all the way in with the Insert key, and click on the map with the mouse. That will train the guns to hit that point on the map. You can then get an idea if you are hitting by watching the text buffer, or, if you are closer, you can zoom in and see the hits.
Adjust as needed.
Hitting sea based targets is a black art. Those that are very good are likely reincarnated souls of pirates, or have a pact with he who shall not be named. We mere mortals hit the E key to go into Sea Mode, SWAG* a distance, and let fly. You can tell by the splashes if the shot was long or short, and if you figured the lead properly. Also, if you get a hit, be a kind soul and say over the range channel what the distance is so the rest of us can stop guessing.
Oh, and if you are shooting at surface targets, make sure to hit the Backspace key to use HE ammo instead of AA. It does a lot more damage.
*Scientific Wild-Assed Guess
