any way to play subnautica with a friend?

the original Subnautica is single player only, there's no co-op setting hiding anywhere. the way people play it together is Nitrox, a fan-made multiplayer mod. it works surprisingly well for a mod but expect the odd desync with vehicles and bases, and everyone has to be on the same game and mod version. Subnautica 2 is being built with co-op from the start, so if you're not in a rush that's the cleaner option.