REWARDS - Respect, $15,000
You'll weasel your way onto the helicopter. When you arrive at the boat, start gunning any men you can see. As the chopper heads to the other side, you get hit by a RPG and the chopper goes down. You are the sole survivor of the crash and you have lost all of your weapons except for your knife. Head to the red marker by the boat and CJ will automatically climb the ladder. The guard says there can't be any survivors and turns his back to you. Use this opportunity to stealth kill him and take his shotgun.
Once you do that, hop onto the lowest box and start climbing the container stacks. Eventually you'll be spotted, so just take out the guard standing on the right side. Continue on your way to the yellow blip, carefully taking out any men that cross your path. There will be a health powerup hidden among the second set of containers. When you reach a large hole that leads into the ship, head around to the other side and use the boxes to go down.
Once inside, you'll see a cutscene followed by 3 guards spotting you. Take these guys out and hop onto the containers to the right of where you entered to find a gun and an armor pickup. Continue your way through this area, killing guards and eventually reaching the container where the refugees are (WATCH OUT for the last guard who will toss a grenade at you first). Shoot the padlock to free the refugees, who tell you that Snakehead is on the bridge.
Head back out to the top of the ship and make your way towards the front. As you approach the bridge, there will be a guard right in front of the entrance. Make your way up the steps, keeping in mind that two guards will be at the top of the first flight. When you get to the bridge, Snakehead will toss you a katana and you must fight. Simply target him and quickly hit him a couple times to kill him. After that, head back outside and meet with the refugees, who are thankful that you saved them.