Escape the island
Follow the Lev and Yara until you cross a bridge towards a hut, then go inside to find some Supplements, now continue following them to reach a building. Go through to the other side and go under the door to reach the street, then head into the next building ahead.
Here you'll want to go upstairs to find some Scrap and Supplements scattered around, then exit the building and go left to find a Coin 32/32 behind the trolley, now go into the next building and climb through the window to view a cutscene.
Find all coins
After the cutscene, look around the warehouse for Supplements and Scrap, then climb through the window and sneak around the building ahead to take down the WLF Soldiers. Now head through the door and get Lev to push down the ladder ahead, then climb up and drop into the building.
Make use of the workbench, then head outside and sneak through the grass to reach the building whilst the Scars and WLF are attacking each other. Once you've made it, grab the horse outside and follow the path ahead to reach Haven.
Eventually, you'll lose the horse and need to continue on foot, so head into the village and sneak through the huts whilst the WLF and Scars are fighting again. Once you've made it through, climb up the hut to the left of the flames, then carefully walk along the pillars and drop down.
Move the wood that's blocking the door to allow Lev to get through, then try and crawl out. Here you'll need to do another quick melee fight, so only go in for a couple hits at a time and make sure to dodge his three swings before striking again.
After you've both fallen down the area below, press [Square] until you can pull out the arrow out with [R1], then Abby will finish him off. Finally, walk under the dock to find a boat, then push it out for a cutscene.
Return to the Aquarium
Once you and Lev have made it back onto land, head into the main room of the Aquarium to view another cutscene.