MAIN MISSION #35 - The Merryweather Heist
EMPLOYER: Trevor (Heist)
PREREQUISITES: MM #30 (Minisub)
1. Headshots: Kill 12 enemies with a headshot.
2. Accuracy: Finish with a shooting accuracy of at least 80%
3. Ninja: Kill 12 enemies using stealth attacks.
4. Container Hunter: Find the container within 60 seconds.
5. No Alarms: Get to the ship interior without being detected.
Visit Trevor's safehouse (for example as Michael) to start this heist. You'll first have to drive Franklin into position. After this, take out the two guys on the freighter with headshots.
As Michael, sneak around the ship while you plant the bombs at the indicated spots. This isn't too hard, but you'll want to avoid being seen. Take out any enemies as soon as possible, preferably with headshots to save Franklin as much trouble as you can. After setting the first three bombs, move to the ship's stern entrance and go upstairs. Michael will take care of the last bomb by himself.
As Franklin you'll now have to snipe a great deal of enemies, including a pilot chopper. Aim for their heads as much as possible and keep track of how many headshots you still need (out of 12) for 100% completion, then take out the enemies regularly when you've reached that amount.
Quick dive towards the device as soon as you gain control of Michael. When he's located it, all you have to do is get Trevor to fetch it with the sub. Hover over the blip (check your minimap) and lower the submarine to attach it, then make your way to the other side of the docks to finish this mission.