This quest begins on the Isle of Quel'Danas from Vindicator Kaalan. You'll find him inside of the newly acquired Sun's Reach Armory. He sends you back over to Ayren Cloudbreaker for a Dragonhawk to use. If you remember, he's the same Blood Elf you spoke to for the quest Distraction at the Dead Scar.
Yes, this is another 'bombing run' quest, though slightly different. Your goal is to bomb the three Elven Destroyers just off of the coast and kill six Dawnblade Reservists to... well, intercept reinforcements. When your dragonhawk takes off, it'll fly past each of the three boats(Dawnchaser, Blood Oath, and Sin'loren). You'll use the Flaming Oil provided to you by the NPCs, and throw it at the sails of the ships. Big, easy targets. You should have more than enough time to hit them all. Eventually your dragonhawk will land on the Sin'loren, where you begin slaughtering Blood Elves again. You can migrate over to the other two ships, but your ride back is on that particular boat. You chat with the dragonhawk when you're done because he was kind enough to wait for you, and you're taken back to the mainland.
You should have no difficulty hitting all three ships with the Oil on one pass, and while the Dawnblade Reservists aren't especially numerous, they respawn very quickly. This quest should only take you a few minutes assuming there aren't dozens and dozens of people trying to do the quest at one time.
For your minor inconvenience of needing to sit astride an undulating dragonhawk yet again, you will receive 7 gold, 59 silver, and 250 Shattered Sun Offensive reputation.
Once Phase 3 of retaking Quel'Danas is complete, this quest will be renamed "Keeping the Enemy at Bay," but the objectives and road to completion remain the same. For more information on this quest and others, you can check out Wowwiki or Wowhead.