Yusuf Wants you to steal a military grade helicopter from a yacht out at sea.
Military Grade Shit
Grab a vehicle, or a taxi and make your way to the docks. Once you get there, grab a boat and make your way out to sea to the yacht. You'll be told you go quietly to avoid bringing attention from the patrol boats, however you can just avoid the boats. Once you get close to the yacht, jump out and swim to the back of the boat and climb aboard.
After the cutscene, head up the stairs and get into the helicopter. Start to fly away, but Yusuf will tell you to destroy the yacht, so don't fly too far away. You can push X to fire rockets and hold A to fire the minigun, however there is no auto-aim or lock on ability, which makes it pretty hard to use. The helicopter does however have much improved handling compared to other helicopters in GTA4.
Fire about ten rockets that make contact with the yacht then it'll blow up and sink. Unfortunately the people onboard somehow survived and they're escaping in patrol boats.
You need to chase after them and take them out. As previously mentioned, the aiming with the helicopter is pretty difficult, but the game suggests you use the miniguns to take out the boats. Don't get too high because it makes it harder to aim, but if you get close to the boats, watch out for RPG's.
Keep chasing the boats and spraying bullets and rockets at them until you've eventually taken them all out.
Once they're all dead, fly the helicopter to South Algonquin and land it on a helipad at the top of a medium skyscraper.
Mission 100% Completion Criteria
In order to get 100% completion for this mission you need to fulfil the following criteria:
- Time: 06:00
- Player Damage: 0%
- Boats Destroyed: 4
Mission 100% Completion Tips
The time limit is probably going to be the biggest problem on this mission, mainly because aiming the helicopters guns is a pain. Drive fast to the boat, speed out to the yacht, climb aboard and run up to the helicopter. Fly away towards the Statue of Happiness until you get the call with Yusuf, then turn around. Shoot the patrol boat next to the yacht, as you'll need to destroy that for the '4 Boats Destroyed' objective, then spam rockets into the yacht until it blows while didging RPGs. After that just chase the boats, keep low and try to take them out as quickly as you can with the minigun while dodging more RPGs. There's not really any more clear advice which can be given, it's all down to your accuracy, or luck as the case may be, with the helicopters guns. It is possible to take out the yacht in one, rocket-spamming pass.