Once the mission begins, fast travel to Amanaki Outpost and grab a vehicle. When you get into a certain range, the mission will update. You cannot be detected at all during this portion, otherwise you will fail. You need to take out the radio operators and get their intel, but you must do it stealthily. Take cover as best as you can, preferably on the hill nearby, then take out your camera and scout the area.
The radio operators are marked with a yellow marker, but there are also normal enemies walking around as well. Use rocks to distract the closest guard near the containers on the left side, and when you get a clear shot, use a Takedown on him. Lure the second guard to the container near the ship and do the same thing. Go inside the ship and lure the radio operator into the ship, to a spot where you can Takedown him. Loot his body for the intel.
The other two operators are on the other side of the big ship, and each one has one normal enemy with him. Remember to use your camera to pinpoint their location, then use all of the debris and containers as cover to hide. Throw rocks to distract the normal enemies to a spot where you can use Takedown on them, then do the same with the operator. Once you have all three pieces of intel, go to the control room of the Medusa.
Inside the control room, you need to go to the radio and you’ll overhear some radio chatter. You’ll hear about some men coming to investigate the area, and you’ll need to take them all out. There’s no reason to be stealthy anymore, so use your height advantage on the ship to take down all of the enemies that come. You can lure some onto the ship and steal their guns, if you need more ammo. Once all of the men are dead, Dennis will call you and tell you to get back to Amanaki Village.