While it may seem like the same plot of the first title, there are a lot of differences between Subnautica and Below Zero. RELATED: Subnautica: Below Zero Should Look to Mods for Improvements Before Launch A stranded scientist must use all of the tools at her disposal to survive and uncover the secrets of 4546B. The sequel provides the same underwater exploration experience as the first. Subnautica: Below Zero has been in early access for over two years at this point. The long-awaited sequel to Subnauticais officially releasing this May.