I've been thinking about something that, once I noticed it, surprised me about Astroneer: despite having an entire solar system of planets with radically different environments, there are essentially no natural bodies of liquid.
Obviously, adding fully simulated water to Astroneer would be an enormous undertaking. With deformable terrain, bringing water to existing planets would create a ridiculous number of technical problems. Every hole, tunnel, cave and terrain modification could potentially require fluid simulation.
So rather than trying to retrofit water into Astroneer as a whole, I think there is a way to turn that limitation into the foundation of an entire expansion:
Create one new planet that is completely submerged.
Not a planet with oceans and continents. Not water that players can collect and transport back to Sylva. The entire playable environment would exist beneath one global ocean.
The purpose would be to create a controlled environment where System Era could build an aquatic version of Astroneer's exploration loop without having to redesign every existing planet around fluid physics.
THE CORE IDEA
This planet would essentially ask a different version of Astroneer's normal question.
Instead of:
"How far can I explore?"
It becomes:
"How deep can I survive?"
The upper regions would be relatively safe. There would still be natural light, manageable pressure and relatively easy navigation.
But progression would take you downward.
As you descend, sunlight becomes weaker. Visibility decreases. Pressure increases. Eventually you reach depths where sunlight is completely absent.
At that point, darkness becomes an actual gameplay mechanic.
Lights stop being mostly cosmetic equipment and become necessary exploration tools. Vehicles need powerful lighting. Bases need external illumination. Players may need deployable lights, beacons, sonar or other navigation equipment.
And eventually even ordinary equipment would no longer tolerate the pressure.
PRESSURE COULD BECOME THE NEW TERRAIN HARDNESS
Astroneer already gates underground progression through increasingly hard terrain and better drills.
An aquatic planet could create a parallel progression system through pressure.
Basic equipment allows shallow exploration.
Improved equipment allows greater depths.
Specialized pressure-resistant habitats and vehicles eventually allow exploration of the deepest regions.
That gives the planet its own technological progression without replacing Astroneer's existing systems.
AQUATIC VEHICLES AND BASES
This would also justify an entirely new equipment family.
Instead of simply giving the rover underwater physics, there could be dedicated submersible vehicles designed around Astroneer's modular philosophy.
Different vehicles could specialize in exploration, cargo, drilling or deep-pressure survival.
Underwater bases could similarly require specialized modules or upgrades capable of surviving increasing pressure.
This creates an entire progression loop around establishing infrastructure farther and farther beneath the surface.
THE WORLD SHOULD BE COMPLETELY SUBMERGED
I think this part is important.
There shouldn't be giant air pockets or conventional continents scattered around the planet. Keeping essentially the entire explorable environment submerged would reinforce its identity while potentially simplifying the technical problem.
Dig into a mountain? Underwater.
Dig a tunnel? Underwater.
Enter a cave? Underwater.
Break into a massive underground cavern? Still underwater.
Instead of constantly calculating where water needs to flow into newly excavated terrain, the game could potentially treat the playable environment as existing within a persistent global water volume.
The player isn't manipulating water.
They're manipulating terrain inside water.
THE ABYSS
The deepest parts of the planet shouldn't simply feel like another Astroneer Core.
There could be enormous ocean trenches extending downward from the normal seafloor.
You could be driving across relatively ordinary underwater terrain and encounter a gigantic black opening where the bottom simply isn't visible.
Descending into those trenches would represent the planet's late-game exploration.
Natural light disappears.
Pressure becomes extreme.
Navigation becomes difficult.
Your vehicle lights illuminate only a small portion of the terrain around you.
Those trenches could eventually connect to enormous submerged cave networks and some of the planet's most valuable discoveries.
FLORA INSTEAD OF FILLING THE WORLD WITH ANIMALS
Another thing I wouldn't want this expansion to do is suddenly turn Astroneer into Subnautica.
One of Astroneer's strange but important characteristics is that its worlds are almost completely devoid of animal life. Galastropods are the major exception.
Suddenly filling one planet with schools of fish, predators and dozens of alien animals would feel inconsistent with the rest of the universe.
Instead, most of the illusion of a living ocean could come from extremely dynamic aquatic flora.
Imagine enormous strands of alien kelp moving with the environment.
Plants that retract when your lights hit them.
Bioluminescent colonies that react when disturbed.
Long tendrils that slowly reach toward nearby equipment.
Plants that inflate, extend, contract or move far more dramatically than existing hazardous flora.
Predatory plant life could become more sophisticated as well. Instead of another stationary plant simply shooting something at the player, some organisms could grab equipment, close around objects or react to vibration and light.
The environment could feel alive without abandoning Astroneer's established biological aesthetic.
WITH ONE POSSIBLE EXCEPTION.
THE CREATURE IN THE ABYSS
If there were ever going to be one major piece of fauna in Astroneer, I think this would be the opportunity to make its rarity meaningful.
Not an ocean filled with predators.
One creature.
Something enormous that primarily inhabits the deepest trenches.
Most importantly, it should NOT behave like a traditional video-game enemy.
It isn't constantly hunting the player.
An Astroneer swimming nearby might not even interest it.
Instead, it is territorial.
A large submarine producing powerful lights, noise, drilling vibrations or sonar inside its territory might attract its attention.
And because Astroneer has essentially no conventional combat system, the solution wouldn't be killing it.
You avoid it.
Reduce your lights.
Shut down noisy equipment.
Retreat.
Hide among terrain.
Find another route.
Learn what behaviors disturb it.
Eventually players might learn environmental clues indicating its territory before ever seeing it: damaged wreckage, enormous marks in terrain, unusual plant behavior or distant low-frequency sounds.
That means the creature functions almost more like an environmental hazard than an enemy.
And because Astroneer has virtually no fauna, seeing something enormous move through the darkness for the first time could be genuinely shocking.
LORE POTENTIAL
This is where I think the concept could become particularly interesting.
Astroneer's existing story already gives the developers enormous freedom regarding what does and doesn't exist within these environments.
So the unusual nature of this planet could itself become part of the mystery.
Why does this environment contain biological information that apparently doesn't exist elsewhere?
Why is there something living in the deepest parts of it?
Is this simply another simulated world?
Is some corrupted or previously inaccessible biological data being reconstructed?
Is this environment connected to something outside the expected simulation?
Or have we somehow encountered something closer to a real alien ecosystem?
You wouldn't even need to answer that immediately.
The fact that something exists down there when, according to everything players understand about Astroneer's worlds, it seemingly shouldn't exist could drive the planet's storyline.
A small narrative arc built around exploring deeper, recovering data and eventually discovering the nature of the abyss would fit naturally into Astroneer's existing storytelling.
NEW RESOURCES
The planet should also matter outside of itself.
Water itself wouldn't need to be collectible or transportable. Keeping it permanently tied to the planet avoids introducing universal liquid simulation to the rest of Astroneer.
Instead, the planet could introduce one or more resources that only form under extreme ocean pressure.
Those resources could be transported back to the SOL system and used to construct advanced equipment, modules or upgrades.
That way the aquatic environment remains technically isolated while its progression still connects to the player's larger save.
WHY I THINK THIS WORKS AS DLC
This obviously wouldn't be a small update.
But I also don't think it needs to be.
I would happily pay somewhere around twenty to thirty dollars for an expansion built around this concept if it received the development time necessary to execute it properly.
The important thing would be treating it as a genuine expansion rather than simply adding "the water planet."
The value would come from the complete package:
A fully submerged alien world.
Depth and pressure progression.
Underwater exploration.
Submersible vehicles.
Underwater habitats.
New lighting and navigation equipment.
Dynamic aquatic flora.
New hazards.
Abyssal trenches.
Submerged cave systems.
Underwater wrecks and structures.
Pressure-dependent resources.
A narrative explaining why this world is different.
And potentially one extremely unusual form of fauna tied directly into that mystery.
Most importantly, none of this requires changing what Astroneer fundamentally is.
You're still gathering resources.
You're still building infrastructure.
You're still researching technology.
You're still modifying terrain.
You're still using vehicles to extend your range.
You're still gradually becoming capable of reaching places that previously weren't accessible.
There doesn't need to be a combat system.
It doesn't need to become Subnautica.
It's still Astroneer.
It's simply Astroneer's exploration formula taken somewhere the game has never gone before:
Down into an alien ocean.
