Synth Retention: The Institute

Follow this Fallout 4 guide to clear the flotilla at Libertalia, defeat the rogue Synth leader, and recover Gabriel with X6-88. Includes tips and rewards.

Walkthrough:

1. Speak with Father in the Institute after meeting the division heads. He will task you with hunting down a rogue Synth who is leading Raiders.
2. Agree to the mission and head to Nahant Wharf to meet the Courser, X6-88.
3. Loot any Raiders X6-88 may have already dealt with and speak to him to begin the assault on Libertalia.
4. Head south to Libertalia, a collection of ships. Clear the initial Raider defenses, using sniping if possible.
5. Cross the narrow bridge to the main area of Libertalia. Shoot down the spotlight.
6. To the left, find a prison area. Pick the Expert lock to access loot, including an Advanced safe.
7. Head up the steps for an ammo box and a vantage point for sniping.
8. Continue right, following the flotilla, to a boat with stairs. Snipe from here and take out the turret. An ammo box is also present.
9. Proceed to another boat with stairs. Snipe any Raiders you can.
10. Reach a boat with two sets of stairs. Pick the Advanced lock on the cabin door for loot.
11. Enter the large, multi-story boat. Clear any remaining Raiders. Loot the kitchen for a Duffel Bag and find chems and meds in various boxes.
12. On the second floor (east side), find wooden stairs leading up. Follow them to an Advanced safe.
13. Continue south. On the red ship, check the cabins (both ends) for an ammo box and a First Aid Box.
14. Snipe Raiders on the next ship to the south. Be aware of a turret on the bow.
15. Near the turret, find a path southwest leading to a beach with Frag Mines. Disarm them if desired.
16. The next boat has a First Aid Box in the cabin and a cooking station. X6-88 will wait for you here.
17. Return to the main flotilla and sneak towards the large boat, avoiding the Raider with the Fat Man.
18. Loot the bodies and head left to a large floating platform with cages. Loot the area.
19. Continue north to a narrow walkway.
20. At a path split, head left to explore a boat for goodies, including an Expert safe.
21. Head right and kill any Raiders. Find ammo boxes in a shack.
22. Locate a Weapons Crafting station and a button to activate transport to the main ship.
23. Use the transport. On the first floor, kill the two Raiders and loot the area. Stairs to the west lead down to a boat with a box.
24. Go up to the second floor, kill the two Raiders, and loot.
25. Continue up to the third floor via stairs to the west. Kill the Raider. On the walkway to the north, find a U.S. Covert Operations Manual on a table.
26. Go up to the fourth floor. Loot the many bedrooms, boxes, and meds.
27. Access the