Subnautica: Below Zero is already a tantalising new twist on the original game

200m away is an Interesting Hole. I know this because I put a beacon in it and labelled it “Interesting Hole”. This is because when I found the interesting hole—actually a promising series of openings leading further into in a biome of beautifully twisting rock formations—I was low on food, water, and health. I needed to swim back to the safety of my little survival pod and sort myself out before braving an interesting hole. 

Below Zero is the spawn of 2018’s success story, Subnautica. Subnautica is a spectacular alien underwater survival sandbox from Unknown Worlds. Below Zero is one of those "expandalone" projects where the developers can work on ideas related to the main game, but in a separate space, so without the same constraints and without the risk of disrupting the original. 

Below Zero is set a year after the events of Subnautica and therfore builds on that game's story arc. In case you haven’t played or haven’t finished that, I'll put a few broad impressions here, so you don't risk spoilers.

It’s so good! There are baby alien penguins! There are new biomes to explore! There are new Interesting Holes to accidentally run out of oxygen in! There are new fish! The story bits that are in place are really promising and seem to be heading in a really interesting direction! 

But it also feels like Subnautica! It has the same core loops, and types of tech. You collect titanium, copper, bits of kelp and so on, then return to your habitat’s fabricator to turn them into tools, fabric, parts, diving equipment. Gradually you are able to go further, faster, deeper. You finally start to have a surplus of materials instead of living a hand-to-crafting station existence. Realising I'd started to stockpile potable water (somehow filtered using a bladderfish) instead of instantly gulping what I’d made was a lovely moment of feeling like I’d gained a foothold on the world. 

Familiar mechanics, like hovering over a plant which produces air bubbles to refill your oxygen while underwater, return in slightly different forms. In this case the bubble plants are replaced by arctic equivalents—a fish you can basically huff from, and a plant with a translucent sac that gradually fills with air which you can use for a small puff of O2. 

You can be harmed, killed or surprised by some of the same things as in Subnautica (bonesharks are back, as is getting lost in a cave system and realising you forgot to refill your backup oxygen tank), but there is also now a creature which can straight-up punch you, and something which I decided to catch with my hands and which either stings or stabs you. Either way it went badly.

The whole sense is of a world you already know, but with regional variations in the flora and fauna, and a year’s worth of slight changes at Alterra (the company you work for) both in the corporation’s understanding of the world and its tech.

Unknown Worlds warn that "Below Zero is full of bugs, runs poorly, and includes only a small portion of our planned features." It’s sensible to set Early Access expectations for those who might otherwise dive in, hungry for more after mining out Subnautica. But my experience was far more robust than that disclaimer might suggest. 

Some animations are a bit weird, some of the assets are clearly placeholders, some of the voiced lines and the subtitles don’t match—that kind of thing. But there’s ample space to explore (my save is bristling with beacons announcing 'BARREN BUT SALTY', 'Cave?', 'Bring Scanner' and about a hundred other memos), and it offers a great sense of the planet beyond the original game’s limits. 

The only technical problems I encountered were a couple of crashes. One came unexpectedly and served as a reminder of the necessity of saving frequently. The other I’d guess was a result of me hammering the in-game screenshot button approximately a million times to get a good shot of the lightning effect during an electrical storm on the planet. 

So it’s a little rough around the edges, and I reached the limit of the current story content after about four hours. I might play a bit longer so that I’ve explored as much as this early slice can show me, but after that I’ll be doing what I did with Subnautica’s Early Access run, keeping tabs on general development but saving the specifics for when they’re ready for a full release.

You can definitely pick up Below Zero having not played Subnautica. But to do so would immediately immerse you in a narrative which builds on the original’s reveals and surprises. It wouldn’t ruin the earlier game’s story, but it would change the experience substantially. So if you’re considering Below Zero and haven’t played Subnautica, play Subnautica.