This probably won't come as much of a surprise given how many teasers and concept artwork we've been shown so far, but Unknown Worlds have just announced a chilling new standalone expansion for Subnautica - Below Zero. It'll offer a brand new storyline set in the Subnautica universe, and will take place in the ice-bound region of planet 4546B after the events of the original game.

The details are still few and far between, but Unknown Worlds have confirmed that the core gameplay mechanics such as base-building and open-ended exploration will still be the focus of Below Zero. They're also tinkering with the idea of adding more voiced dialogue to better flesh out the story, as well as introducing thermal management as a major gameplay mechanic. Since Below Zero is still early in development none of this is set in stone, but it should at least give you an indication of what direction Unknown Worlds wants to take Subnautica in.

Much like its predecessor, Below Zero will release unfinished into Steam Early Access, after which the cycle of content updates and balance changes will shape the final game based on community feedback. In most cases the presence of Early Access would worry me greatly, but given how well Unknown Worlds have treated Subnautica I think its safe to say that Below Zero will end up being pretty good as well. I'd still recommend avoiding Early Access as you'll just spoil the experience for yourself with an unfinished version, but each to their own I suppose.

Once more information breaks through the ice I'll make sure to let you know, but until then you can check out the official Trello board to find out what the developers are currently doing. It's essentially a list of features and modules they're working on, so while it might contain some spoilers, it will give you a pretty decent idea of the shape Below Zero is currently in.