Subnautica

EDIT: There seems to be a delay for this achievement to pop. Please allow an overnight delay irl before expecting this achievement to unlock.

EDIT [20 Dec 2021]:

Based on recent comments… it sounds like the Subnautica opening sequence has changed.

I completed Subnautica years ago, so I haven’t seen how the opening sequence unfolds in its current form. My apologies for this.

But this is a straight forward unmissable achievement, so this won’t complicate the solution.

Solution
As long as you get into the sea / exit your Lifepod for the first time at the beginning of the game, this achievement will unlock.

Original opening sequence
In the original state of the game, the opening sequence had you buckling in to your Lifepod whilst the Aurora is crashing on to this unknown planet. The crash landing gets chaotic, and a metal panel gets ripped off the wall and hits you in the face, causing you to blackout.

When you wake up, your Lifepod was on fire, and there’s a fire extinguisher you needed to use to put the fire out.

Once you’d extinguished the fire inside your Lifepod, you were then able to exit the Lifepod for the first time. Which popped this achievement.


Original Solution:

Very easy and unmissable achievement.

Play on Survival, Freedom or Hardcore Mode.

After the opening cutscene has ended you will regain consciousness to find your Lifepod is on fire. Pick up the fire extinguisher off the floor and use RT towards the flames to extinguish them. Your fire extinguisher has a limited usage so don’t be wasteful with it.

Now you can go underwater for the very first time, and this achievement will unlock.

To go underwater you’ll need to exit your Lifepod. You can exit your Lifepod two ways.

You can interact with the ladder in the middle of the Lifepod to climb up it and exit through the door at the top of the Lifepod. You will then need to dive down into the water.

Or you can interact with the door on the floor to exit through the bottom of the Lifepod. You will immediately be underwater by exiting this way.

Please Note: I was playing on Freedom Mode (similar to Survival Mode, but without the requirement to maintain hunger and hydration levels).

All achievements can be obtained in Freedom mode.