From Quincy to Spectacle Island

Poseidon Energy (Exterior): Clear Raiders on the catwalk by heading north to find a way up. Loot the trailer on the roof. To enter the building, either pick a [Master] lock on the roof or on the west side, or swim through pipes on the south-eastern side into the "Poseidon Energy Sublevels".

Poseidon Energy Sublevels: Head inward, looting a dead Raider's Duffle Bag in the pipes. Emerge to a catwalk, clear the northern room's Mirelurk, then proceed south-west, clearing another Mirelurk and finding a nest and First Aid Boxes in a room. Continue to a larger submerged room with two Mirelurks, a laser turret, and another Mirelurk Nest; loot the Toolboxes. Head north-west to a room with a [Novice] terminal that opens the door upwards. Clear the laser turret and Protectron, then loot the room. Continue north-east, take out the ceiling Laser Turret, and proceed to another room with a Laser Turret and Protectron. Loot the southeast cubicle's [Novice] safe. Continue to the door leading to "Poseidon Energy" proper.

Poseidon Energy (Interior): Loot the [Novice] safe in the northwest corner. Use the [Novice] Security Terminal to open the security door. Destroy the ceiling Laser Turret and the Protectron to the north-east. Proceed down the hallway, disabling the Laser Turret at the path split. The left room is a bathroom with a First Aid Box. Continue, taking out the next Protectron and disarming frag mines. Sneak past the patrolling Protectron and turret to the southwest break room. Destroy the Laser Turret and pick the [Novice] door lock. Follow the hallway, disarm a can trap, and avoid a Frag Mine guarding the stairs. Head up the stairs, looting the first room for chems. Continue to the next room. Loot the north room's First Aid Box. Prepare for a fight. Snipe the south hallway turret if desired, but expect an Attack Dog. Defeat the Raiders and the named Raider "Cutty" (in Power Armor). Loot Cutty for the "Poseidon Energy Key". In the same room, find the Endurance Bobblehead, Tesla Science magazine, a Steamer Trunk, a First Aid Box, and Ammo Boxes. Continue south, looting another ammo box. The south exit leads to the roof. The north path leads to two more Raiders. Head north-east to loot a "chem room" and use the chem station. Return and head southwest to the roof access, which is a [Master] lock. Exit the facility.