If you read the threads Fugi linked to above, hopefully you understand how to switch between land and sea modes (Shift+Q and Ctrl+Q, respectively). After rereading those, here are few other things that came to mind:
Some important aiming tips:
To hit moving enemy ships, you need to have the correct range (adjusted vertically by pushing or pulling your joystick - y axis) AND correct lead (moving the sight left or right of the target - using the joystick x axis). Remember in Sea Mode, you are essentially aiming for a point on the water a set distance from YOUR ship. You need to adjust your aim so the rounds impact this point as the enemy ship reaches it.
The quickest way to determine range, is to simply line up the bottom of the numbered yellow hash lines with the waterline of the target ship. However, some correction is needed if the target if moving toward you or away from you.
If their ship is moving TOWARD you, your aim point (on the water) needs to be CLOSER than the enemy ship is at the moment you fire. Conversely if the ship is moving AWAY from you, you must add some distance so the rounds fall further away, where the ship will be when the rounds get there. Essentially, you have to allow for the time of flight of the rounds. Range therefore plays a big part in determining how much to adjust the range for ships moving toward you or away from you. (This is also true when using the Shore Battery.) You need to get good at zooming in and determining if the ship is closing or extending from you, even at an oblique angle, in order to adjust your lead in the range (vertical) component.
Likewise correct lead is also determined by the direction of travel of the ship left or right of your point of aim. With 8-inch guns, if the target is broadside to you (moving either directly left or right) try starting with a lead amount of about 10 in the aiming reticle. In other words, put the yellow aiming reticle completely ahead of the enemy ship, with the 10-line just touching the bow (and the bottom of the hash-marks at the waterline, as mentioned above). Again, this is also range dependent, but this starting aim point seems to work well as a baseline for most ranges CV combats take place at. Bear in mind though that this is a "fast and dirty" estimate, and you will need to watch the fall of your rounds and adjust your lead accordingly, especially if the enemy is changing course.
Like all shooting, practice is the key. You can go offline and practice, or there are ships in the Traing Arena specifically for practicing this. If you see me in game, hit me up if you'd like to go in the TA for a walk-though of using the various guns, as hands on practice is better than any write up. If I'm not particularly busy, I'll be happy to walk through some practice and help you adjust your aim with specific targets.
A few other tips about 5-inch guns:
5-inch guns have both AA (anti-aircraft, proximity fused "puffy ack") and HE (high explosive) rounds. Anti-aircraft is the default mode when you get into a 5-inch gun. So, when firing 5"ers at ships, remember to switch to HE rounds using your Backspace key, which toggles between the ammo type.
If you are in Sea Mode firing HE at ships or shore targets and you spot an aircraft you want to shoot at, quickly hit the "Q" key and then the backspace key; this will put you back in manual aiming mode and switch you back to the AA rounds.
Because of the rate of fire, the dual 5-inch guns can be very effective at sinking ships, killing town buildings and hitting fields or even destroying a shore battery, once you learn how to aim and hold on your target so you can land round after round. When firing at land targets, use land mode, click on the map and then zoom as far in as you can to spot the fall of your rounds. With some practice you will be able to target specific objects like radar, ammo bunkers and field guns. (This is even easier to to with 8-inch guns, but the 5-inchers are effective too with some practice.)
When firing at ships with 5-inchers, there is a higher ballistic arc than the 8-inch guns, so 5-inch guns require more lead, often double the amount, that the 8-inchers do, so they require more practice. One way to measure your longer range lead is to put your grey "viewing crosshair" (controlled by the mouse) directly on top of the gold reticle. This will give you a wider reticle with more hash marks to adjust your fire. Even though it's a bit more difficult, even the single 5-inch guns on the DD's can be effective against ships and ground targets, as well. Don't underestimate them.
A single 5-inch HE round will kill a PT boat with one hit, so the dual 5-inch mounts on the CV and CA are good for those pesky PT-ers that launch after you've sunk their battle-group. Remember, once you've sunk all 6 ships in a battle-group, the PT boats can still spawn for 10 minutes after the CV was sunk (at which point all the ships respawn at that CVs home port). PT's will spawn as though the CV was still there, so if the CV was closing and moving right to left, the PT spawn will be moving the same way (although the CV course is still movable). Usually the PTers will do their best to get their PTs spawning as close to your ships as they can, so after all the boats are sunk, watch for PTs too!
Although the CV spawns back at its port in 10 minutes, the support ships, Cruisers (CA) and Destroyers (DD), have a downtime of 60 minutes. If the Carrier remains up for sixty minutes after any of these are sunk, they will respawn at the Carrier's location -- like replacement vessels. This is important to note, because there are cases (like when capturing a port with the attached CV near by) when you may want to sink the support ships first (always kill the enemy cruiser first!) but leave the CV up until you capture the port or are close to doing so. Then when the CV respawns in 10 minutes, your side will own it (if you still own the attached port).
That's all the tips I can think of at the moment. Again, hit me up via PM or in game if you'd like a personal tutorial in the TA some time on using the various guns, including the 88 (my personal favorite!).
<S>
Ryno