This is not so much of a strategy as it is a series of tactic:
Fire Support Carrier
1. Equip carrier with shells in the main gun
2. Position a manta high above the battlefield
3. Remember the elevation on the main gun and fire
4. Switch to manta to track fall of shot and adjust accordingly
"Walking Barrages"
1. Set up carrier and manta observer
2. Imagine your target area as being in a rectangle on a grid, aim for the lower left corner and find the elevation required to hit it.
3. Fire salvos at the elevation on different angles from the bow of your ship until you have carpeted that area with fire
4. Raise the elevation on the gun by one degree and repeat step three
5. Repeat 3&4 until the area is a smoking ruin
Obviously, it works much better during daylight hours. Very simple and a great way to soften up those "Deadly" islands or take out scramblers/shield boosters/radars. The main gun has tons of ammo and firepower, so you can easily use this to soften up an enemy position. I recommend using it to attack positions that are simply too heavily defended to attack head on, or if you need to eliminate a single target quickly without exposing your units to danger. Once you get used to this, you can very quickly disable an enemy's key structures, I like to attack in this order:
1. Radars
2. Scramblers/Shield boosters
3. Manta garages
4. Missile Turrets
5. Heavy anti air
6. Walrus garages
For me, the key is to soften up the area quickly so I can send in heavy mantas to wipe out resistance and drop a hacker walrus (great mental image right there...) to take care of fire walls and command centers. I do recommend being careful at first in order to avoid accidentally destroying command centers or firewalls. On the other hand, if you want to remove an enemy's command center in a hurry, this is a good way to do it. Also, it works a treat for destroying enemy piers.
Also, another thing I found that works well:
Artillery Rush
This tactic works really well on scrambler islands, I have no idea about firewall islands though so save before trying it there. The nice thing is that destroying a command center also shuts down the scramblers, so you can just build a new command center and move to the next island.
1. Use above tactics to get the enemy command center in your sights
2. Destroy it using artillery
3. Send in a heavy manta (preferably one you are piloting) to clear any resistance
4. Air drop a walrus with a construction module and build your new base
5. Leave
