Subnautica

EDIT: Some achievements in Subnautica seem to not unlock immediately. This can happen with some Xbox Ones titles, and whilst you have completed the requirements to pop the achievement, it just won’t pop for a day or two. Please allow for around 24 hours before panicking about an achievement not unlocking.

To unlock this achievement you need to interact with a Data Terminal inside a large alien facility on an island.

The island you need to visit is connected with the narrative. So it won’t be too difficult to find and reach this island.

Progress the Story
So far you have been exploring, finding new materials, scanning new blueprints, fabricating new items, tools and equipment.

Meanwhile you will also be receiving new radio beacon updates from inside your Lifepod. Continue to interact with your radio whenever there are updates. These incoming radio transmissions will progress your story. Whenever a new radio update is available, you’ll get a radio icon flash up on the top right of your screen whilst you’re out exploring. Once you enter your Lifepod, there’s also an audio indication that a new message is pending in your radio when you’re close to it. And a visual indication - the red light should flash on the radio itself indicating a new message is available.

After visiting a few Lifepods from other survivors, the Aurora (the giant crashed ship)’s nuclear reactor will have ruptured and an explosion will occur. This explosion will now make certain areas radioactive meaning you will need a Radiation Suit to be able to travel to areas nearer to the Aurora. These are indicators that you are progressing through the story.

Sunbeam and the LZ
You will start to get radio messages from a rescue ship called Sunbeam.

Sunbeam are going to try to rescue you, and they will keep you updated with several radio messages. Eventually Sunbeam will announce an LZ where they want you to be prepared to meet them at a certain time. A countdown will now be displayed in-game.

The LZ that the Sunbeam rescue ship confirms is an island. There will be a beacon showing you where you need to travel to.


Reaching the Island, and the Alien Facility
It’s strongly advised you have at least unlocked the blueprint and fabricated a Seaglide at this point. It should be natural progression but if you’ve been speedrunning you’ll want the Seaglide first.

Travel to the beacon indicating where Sunbeam will arrive. As you reach the island, head around the left side of the island and you will eventually find a sandy beach you can step on to. Watch out for the little crab creatures, they jump at you and they bite. They’ll chip away at your health.

If you reach the exact position of the Sunbeam LZ beacon you will clearly see a large alien facility, which has a large door for entry. But there is some type of shield blocking entry. There is a console just outside the door which will prompt you to enter an Alien Artefact. Just on the floor near this console is a broken artifact. It has purple symbols on it which should make it easily distinguishable from most other objects you’ve interacted with on this island so far. You should scan this broken Alien Artefact.


Finding an Alien Artefact
You’re looking for an Alien Artefact that’s still in tact, so that you can insert it into the console and unlock the shield door to the alien facility. Just head up the hill to the right of the door / console and you will soon come across the alien Artefact you need.

Come back to the shield door, interact with the console to insert the Alien Artefact and in a matter of seconds the shield will disappear. You can now enter the facility!


Interact with the Data Terminal
Inside the facility you will walk through some corridors. And very quickly you will enter a larger room and encounter a large Data Terminal. This is the first Data Terminal you’ll see but there are more in the facility. Simply interact with this first Data Terminal and you will unlock this achievement!


Please Note: You should be able to do this before, during or after the Sunbeam Landing countdown. It’s easier to find the island when you get the Sunbeam mission if you haven’t played Subnautica before.

I was playing on Freedom mode which is Survival Mode without the need to maintain hunger and hydration levels. So this achievement is at least unlockable on Survival and Freedom game modes.

Those of you trying to find the mountain island before the objectives or after.
(The sunbeam objective sent me to the other island and not this one)

To find this island, you need to head at these directions.
The compass looks like this: ( a bit exaggerated but it works)
N..|..|..|..|..|..NE

You need to head with your centre at this point:
N..|..|..|..>|<..|..NE
slightly N by NE, 850-860 meters
For the rest of the achievement, i suggest you read the other solution by ell635, They have done a great job, as it pretty much has everything you need.
thanks and i hope this helps