UPDATE (5 Sep 2016): Subnautica will be a single-player game only, and will not receive multiplayer.

Will Subnautica below zero get multiplayer?

The short answer to the question is that Subnautica: Below Zero does not have any form of multiplayer. Players don't even need to have an internet connection to play it other than to download updates. ... Subnautica: Below Zero is available now on PC, PS4, PS5, Switch, Xbox One, and Xbox Series X.

Is Subnautica getting coop?

Officially, unfortunately, at this moment in time Subnautica does not have co-op multiplayer. Over on the game's official forums, Game Director 'Flayra' posted the following message regarding co-op multiplayer in Subnautica.