Escape Dead Island

There are 4 underground areas, which are inside 4 mysterious hatches that are around the island. You probably found them in your first playthroughs, and remember that they required "alpha", "beta", "gamma" and "delta" keycards. Well, with the DLC installed, they just open.

If you have a save in the middle of a playthrough, you don't need to start a new one for the hatches to open. Just make sure that the DLC is installed (you'll see some new options in the main menu if positive, as ShutTheCakeHole has commented) and you'll be able to access the new content (thanks to Darth Chimp for the confirmation).

You'll find a couple of hatches little after starting the game, but in order to access them, you need to progress in the main story until you have the flashlight, which is needed to enter the hatches.


After getting the flashlight, keep progressing a little more until your mission is to get the third of three key cards to the security room. Your mission then will be "Reach the Helipad".

On your way back from Crown's Estate headed to the Helipad, you will cross a tunnel between the Airfield and the Geopharm Labs Exterior. As soon as you cross that tunnel, go forward, and take a right as soon as you can. There will be your first hatch, which is the main hatch with the DLC mission. I don't know if this hatch is required for this achievement, as it isn't "secondary", but you have to access it anyways, so do it. That will net you an achievement:


Complete the tasks inside this hatch, or go outside again, as you wish (I recommend to complete it now). Once you are outside, keep following your objetive, but, when you reach the "Jungle" zone (the one with the two corpse piles), you'll take a slight detour.

Follow the river down, and it will lead you to the path that goes back to the beach. When on the beach, go left, and just after passing the blue container, behind a rock, you'll find the second hatch. Go inside, pick the +1 Medkit, and now, follow the objective marker to the Helipad.

After the elevator sequence, follow the next hallway and you'll see the third hatch in front of you. Hard to miss. Enter and pick the Walloper weapon, netting you the following:


Keep progressing. Don't forget to kill 10 enemies from a distance (say... 25 or 30 meters) with your recently adquired weapon for another achievement. Check my guide on that achievement for details.


Complete the Geopharm Labs mission, and your next objective will be going to the Marina. Do that, and when you reach the storage room where the next item is, don't enter yet. Go to the red fence at the back of the Marina, pass through the hole and go to the end of the shore. There's the fourth and last hatch, and your achievement.

Also, inside is Crown's Audio Log #11, required as a part of another achievement.