Subnautica is a game in which you are one of the few survivors of the Alterra Corporation ship Aurora who crash lands on the unnamed ocean world. Your first few moments are of watching part of the ship detonate through your pods porthole, then being knocked out by loose debris within your pod. After coming to, you deal with a raging fire, and learn you are alone in an ocean and must find a way to survive. You gather resources, food, water, build a base, explore, discover the incredible secrets of the world, and learn what actually happened to the Aurora before escaping the planet. There is a finite amount of resources of titanium, copper, lead, silver, gold, and other metals and crystals. So you must explore to gather more, however there is an abundance of all of them, so you will probably never run out.
The map is lovingly crafted, and it is obvious. The biomes are diverse, and look amazing. The creatures can, and will, scare you. The first time i found a Reaper Leviathan I was terrified because it picked up my submarine, shook it around, and destroyed it. As the game progresses you will have to find fragments of structures, vehicles, or equipment scattered during the explosion and crash of the Aurora. Find enough fragments of a specific items fragments and you can build it (Usually 2-3).
The base construction is easy and fast, and you can make some interesting things with it. As long as you have gathered the materials and the blueprints needed for what you want of course.
Now onto the Cons. My biggest issue with this game is there is no co-op. Especially since one of the vehicles in the game even states it was designed to be piloted by a crew of 3. I think two players would be perfect, and it wouldn't completely destroy the balance of the game because it would double your food and water needs, which are very important in this. My second biggest issue is there is no map. Now I know its an unexplored world, however your PDA has the ability to understand entire complex vehicles and electronics from a few broken parts with the aid of a handheld scanner but it cannot form a basic topographical map. After you get the scanner room you can even get 3D scans of large areas around your base, but cant access it from your PDA for some reason, even when you can get other data from it directly to your visor. This issue is rectified with mods, which I will recommend you check out, it will save a lot of getting completely lost when there is no reason to. Other than that its smaller issues like how sometimes you may not find fragments of a blueprint you need to progress due to the random scattering so you spend a long time searching till you eventually find it, or if you are unlucky (it happened to me) hostile creatures will camp your life pods entrance early on before you can build anything up. So more bad luck than anything.
All in all, its a great game that you can get a long amount of game time out of, but it can be made a bit better. I would put it at a solid Play, especially since there are mods to fix some issues. However, if you are afraid of the dark, deep ocean, or claustrophobic, AVOID THIS! You will encounter all 3 at some point or another.