Absolutely outstanding from the very first second which sets the atmosphere wonderfully, to the final button press. This is not only a great example of how to do early access but how to do everything. The world is handmade over 5 years. Each area crafted with care. Every path intentionally set to provide the adventure of an action exploration game but the choice of an open world one. The survival element is not a big challenge but gives you purpose to interact with the world. Even grinding in this game is fun because of how beautiful it is to just interact in this world. You will have tense moments of action where you have commited all of your resource to a particular action while your surrounded by danger, and these moments are made even stronger by the slower points of collecting resources and crafting and decorating your sea base to make it home.
I can go on and on about how wonderful of an experience this game was. But to summarize my experience with Subnautica: No game has ever made me more sad to finish it.