I don't have it granted,but I've been abosrbing how my friend's doing it. In there first off give your squad commands to kill those ties then fly off shooting some lone ties and occasionally breaking off to shoot the shield generator dishes no top. You should give each one a constant barrage of laser blasts and shoot about 2 or 3 missile at each one while you're blasting. The dishes should fall in one pass(make you fire in rapid mode). And then if some ties chase you,close the s-foils and fly out and turn every which way to lose them(or you could just break and shoot them from there). Anyways then you destroy the command deck. If ya can't find it just tap on your targeting computer at the area of the stardestroyer and look for yellow glowing stuff. The command deck is the yellow rectangle on the top of the Star Destroyer near where the bridge is. After you take it out,the mission ends. And here's a tip if ya don't wanna lose your targeting computer effiecency for those medals: only turn it on for a few seconds either when you can't see some ties in darkness or birght light,or to see the objectives(yellow again) If ya don't use it too much,you'll get the efficiency rating(my bud here only gets down to 95% efficiency that way). Hope that helps. Oh and good luck on the next one,it's a doozy.Though seeing AT-AT in water is very rewarding. And look at the water effects and graphics(the sunset on water is pretty and the AT-AT looks cool cuz the water goes midway up the legs and you see them underwater if ya look hard enough but you can slo see the reflection off the water of it). Okay good luck on it.
"Sir,we are beginning our search for these rumored 'underwater villages'.They will not stay hidden for long". -Battle Droid Commander OOM-9!