No-one in their right mind would have put down money on 'sandbox submarine adventure' being the next project from the creators of human vs alien FPS/RTS crossbreed Natural Selection. I did, however, and as a result I became a billionaire. Unfortunately I then put down a billion quid on Destiny turning out to be Frog Fractions 2 in disguise, and now I am poor again. Swings, roundabouts.
Devs Unknown Worlds have been teasing bits and bobs of Subnautica - for that is the submarine game's name - for a while, but now they have video footage of how badly wrong being full fathom five can be. Here is a fact: a video is like a picture, but it moves and sometimes there is sound too. I hear it's the future.
They say of the above that "This is a technical prototype, and not representative of the quality of the final game. As the water level rises, there is less and less room to hide, and to breath. Perhaps if a submarine is not repaired fast enough, it will sink – And all the hard work that has gone into customising it, all the equipment stored on board, and even your life could be lost."
Clean, Portal/Mirror's Edge-ish lines and colours, and an emphasis on water as implacable force of destruction rather than blue stuff wot you go swimming in. It's too soon to get a real handle on what they're trying to do here, but in theory I'm definitely onboard for something that wants to do so much with an undersea setting. That's one area in which BioShock was weirdly unambitious.
Your best bet of getting a sense of quite what it is Unknown Worlds hope to achieve is to keep an eye on their Trello-based progress tracker here. Granted, it's primarily bits and bobs rather than out-and-out explanation, but it's fascinating insight into how a game gets made - inspirations, borrowed features, performance reports, even who's going to which meetings... Also lots of pictures, which I suspect will be the main draw.