Developer interviews say the new planet's map will exceed Subnautica and Below Zero at their early access launches and reach several hundred metres deep.
Unknown Worlds said the early access world will be incomplete, with some areas locked until future updates, so its initial scope may feel smaller than the finished older games.
The studio expects Subnautica 2 to stay in early access for years, adding biomes, depths and other content over time before becoming the series' largest overall map.
With the iconic Cyclops submarine gone, what massive new vehicle will players command in Subnautica 2's vast oceans?
After winning back control from its publisher, what creative risks is Subnautica 2 now free to take?
With a new BioMod system letting players evolve, will humanity become the ultimate alien on planet Zazura?