Climb the wall, move through the cracks and hop down to the walkway. In the locker room are two packs of [SHOTGUN SHELLS]. Continue to discover the 'Research Lab' camp, which is currently unsafe to use due to the presence of nearby enemies. [DOCUMENT - #4 WARTIME INTELLIGENCE (SOLDIER: AWAKENING)] can be found on the desk with a hopeful message in it. Move around the corner and kill the two Solarii guards, then head back to the camp to upgrade your gear. You can possibly upgrade your bow at this point (to a [COMPETITION BOW]), while your shotgun might be upgradable to a [COMBAT SHOTGUN].
Crack the closed door open and leap to the other side to move through the opening. You can find an [XP BOX] and a [GPS CACHE] here. You can climb through the opening again to return to the hall. Move to the other side and press the button to call the elevator. Since it's jammed, climb the crates and destroy the sprocket with your axe. Climb over to the other side and head upstairs. You can find [DOCUMENT - #1 GPS SECRETS (UNKNOWN: MYSTERIOUS ORDERS)] on some barrels, as well as some [RIFLE AMMO] nearby.
Move up to the fourth floor (you'll come across a [SALVAGE BAG] and some [SHOTGUN SHELLS]) and call the elevator. Head back to the third floor and climb the ladder next to the elevator switch to pry a second cogwheel loose. Now call the elevator at the third floor, move down behind the elevator and leap to the catwalk (which has some [SALVAGE] on it as well). From here you can pry the third cogwheel loose.
The last cogwheel is a little more tricky. Call the elevator at the third floor, make your way to the fourth and look down the elevator shaft. You'll notice a (normal) barricade on the right side; shoot it out with your shotgun. This reveals an opening to a climbable wall that curves around the elevator. Call the elevator (while you're still at the fourth floor) and drop on it just before it moves past the opening. Quickly leap through and climb the wall to a previously inaccessible part of the catwal that also contains some [SALVAGE]. From here you can pry the last cogwheel loose.
Make your way down and look for a sun totem[#1 SUN KILLER] to the right of the elevator (after walking over). There's also an [XP BOX] here. [100 XP]. Go through the cracks and search the immediate left part of the area for a [SALVAGE LOCKER]. There's a [RELIC - #2 HELMETS (CEREMONIAL HELMET)] on the right side, behind some crates. Kill the guard up ahead and a second will come to inspect his body, so get ready to kill him too. There's some [RIFLE AMMO] and a [SALVAGE LOCKER] around the corner. The [GPS CACHE] stashed away behind the crates can be collected by climbing the crates on the right side of the hall.
Research Base all collectibles.
Continue down the bunker to reach an large offering hall. Collect the [SHOTGUN SHELLS] near the blue barrels, and search for some more [SHOTGUN SHELLS] behind other blue barrels in the water (next to the stairway). Approach the corpse at the top of the stairs to watch a scene. Afterward you'll also have obtained [DOCUMENT - #9 ANCIENT SCROLLS (GENERAL: FAILURE OF DUTY)].
Two waves of enemies storm the area. The first wave isn't too difficult, but the second can be tricky. You know when the second wave arrives when some rocks kill on of the Solarii guards. At this point it's a good idea to wade into the water behind the stairs. Although you'll have to defend both sides, dynamite doesn't blow you away here. Use your handgun's triple shot when you run out of rifle ammo and stay on the move between both sides, hiding behind barrels. With all enemies killed, move out over the burning walkway. At the end you'll slide right to a climbable wall that leads back to shipwreck beach.
SHIPWRECK SHORE - BACK AGAIN
You'll find some [SALVAGE] as you head outside. Use a rope arrow to move across, then let the two Solarii guards finish their conversation to waste them with headshots (the one closest to you first). You can find [SHOTGUN SHELLS] and [RIFLE AMMO] on both sides of the path, and some more [SHOTGUN SHELLS] and [RIFLE AMMO] on the lower platform. Slide down the two ropes for a cutscene, then enter the boat whenever you're ready to proceed to the next area. [200 XP].
After you drop down, look around to spot a metal barricade you can blast out with a grenade. Some [SALVAGE] can be found behind it, but there's a second metal barricade above; blast it out and search the room behind it to find a [RELIC - #1 HELMETS (CHOU DYNASTY HELMET)]. A [GPS CACHE] can be found on the left side of the river. Curve aroudn the area and look up to spot a [SALVAGE BAG].