This is a breathtakingly beautiful, challenging, and immersive open-world adventure that grabs you from the start and doesn't let go. Subnautica -- which took more than five years to create -- is highly recommended, especially for those who love marine exploration, crafting items, and puzzle-solving, and a solid story to tie everything together. Also, for fans of horror movies and games, Subnautica does have some terrifying moments. There are some minor technical issues -- such as images that suddenly pop up, and long-ish load times. Plus, those who prefer twitchy action might not appreciate the slower-paced scavenger hunt nature of the game, but Subnautica is really, really good. Also, you can choose to play how you like: Creative mode allows you to explore underwater worlds and build bases without having to worry about health upkeep or resource costs; Survival mode is more difficult, as you must manage health, hunger, and hydration; and the aptly named Hardcore mode only gives you one life and no O2 alerts, to truly test your survival skills.
Once you're in the first of a few different vessels, you'll quickly get the hang of navigation and control, so you can focus on the core gameplay element -- survival -- as you follow waypoints to complete various goals, and choose flight or fight based on the threats that await you (some can't be killed, so you'll need to think of alternative approaches). One of the first memorable moments is discovering and investigating the huge spaceship that brought you to this alien world to begin with. The game is a real stunner, with high-resolution graphics, impressive lighting, and amazing special effects (including very realistic-looking water). Couple that with excellent sound effects -- like hearing the moans of predatory creatures swimming near you -- and professional voice acting and music, and you'll get a sense of the production values here. All in all, despite the few technical issues, Subnautica is an extraordinarily fun game worthy of your time and money.