Once Human Is Turning Your Base Into a Warship in Its Biggest Free Expansion Yet

Once Human has spent more than two years teaching players how to survive a world poisoned by Stardust. Isles of Abyss is about to remove the reassuring part where there is solid ground beneath their feet. The free Ocean Expansion launches on October 21 PT — October 22 across many other regions — and its new Gameplay Trailer finally shows how dramatically the survival loop changes once players begin constructing their own ships, diving through contaminated seas, attacking Voyagers, exploring hostile archipelagos and descending toward an ancient entity known as the Sunken Lord.

Starry Studio describes Isles of Abyss as the largest content expansion Once Human has received since its 2024 launch, and the scale goes considerably beyond adding another region to the existing map. Ships become mobile territories that can be designed almost like conventional bases, ocean resources feed an entirely new Tech progression, different regions impose environmental rules that affect sanity, temperature and equipment durability, underwater exploration requires specialised survival gear and naval encounters eventually escalate into full boss battles involving artillery, weak points and coordinated crews. The trailer's warning is straightforward: the sea is finally open, but almost everything useful in it appears to be trying to kill you.

Your ship is not transportation — it is the new base-building system

The most important addition is freeform ship construction. Isles of Abyss treats a vessel as a movable water territory rather than a disposable vehicle, allowing players to enter Build Mode and construct everything from the overall hull shape to the internal deck arrangement.

Dedicated ship components include hulls, bows, gunwales, decks, handrails, pillars and bulwarks, with square, triangular, sloped and curved pieces allowing players to define the silhouette instead of selecting one predetermined boat model. Wood, iron, steel and alloy variants provide further progression, while ship layouts can be saved as independent blueprints and subsequently placed again.

That fundamentally changes the relationship between exploration and home. Previous Once Human scenarios generally asked players to establish territory and then leave that territory to explore. In Isles of Abyss, part of the territory comes with you. Storage, production, weapons and support facilities can travel across the ocean, reducing the distinction between expedition vehicle and headquarters.

The system develops alongside Tech progression. Early vessels rely on more basic forms of propulsion before unlocking sails, fuel engines and eventually electric drives. Boosters and side thrusters improve mobility, while Auto Cruise allows players to mark a route and let the ship navigate itself. Underwater teleportation, cross-world return-to-ship functions and onboard respawning are all designed to make the vessel the central point around which the scenario operates.

Building the ship is only half the problem — then you have to arm it

The Gameplay Trailer puts considerable emphasis on naval combat, and Starry Studio has built an unusually large artillery catalogue around it. Harpoon Cannons can fire through the water and are particularly effective against marine creatures, Long Cannons specialise in damaging decks and structures, Rapid-fire Cannons are designed around sustained weak-point pressure and Shotgun Turrets cover a wider area against ships and patrol boats.

The arsenal becomes stranger as Tech advances. Frost and Freezing Cannons can interfere with enemy movement, Corrosion Cannons amplify subsequent damage, Rocket Launchers provide sustained barrages and Oil Drum Launchers create enormous explosions and burning zones. Players can also fit a Ram for direct collisions or deploy naval mines rather than relying exclusively on artillery.

The important detail is that ship design therefore becomes tactical rather than purely decorative. A vessel built for long-range Calamity Tower bombardment may want a different layout from one intended to hunt marine creatures or board enemy Voyagers. Gun placement, propulsion, durability and the ability to manoeuvre around incoming threats all become part of the same construction problem.

That should give Once Human's building community an entirely new obsession. A beautiful floating fortress is useful. A beautiful floating fortress that cannot turn quickly enough to avoid a boss attack is considerably less useful.

The archipelago has five regions, and each one wants different preparation

Isles of Abyss spreads its survival systems across five major environments rather than treating the entire ocean as one uniform biome. Fragrant Cape serves as the introductory region, combining coconut groves, rocky shallows, ruined settlements and grounded ships where players can collect the supplies needed for their first real voyage.

Further out, the rules begin changing. Reefshadow Bay combines freezing tundra, reefs and floating ice with the Mist of Deceit, which reduces temperature and visibility. The lower a player's HP becomes, the narrower their useful field of view gets. Mist Core Grass provides materials that eventually feed back into ship ammunition and electricity production.

Misty Marsh introduces the Black Tide, where Stardust contamination directly attacks Sanity while simultaneously producing valuable resources used in diving gear and water facilities. Spring Valley is affected by Time Rain, which rapidly drains Energy and Hydration while degrading equipment durability, but also accelerates crops and animals and creates valuable production materials. Finally, Falling Ember surrounds an active volcano and its Skyfire phenomenon, where incoming meteors damage players and structures, raise temperatures and sometimes spawn enemies guarding deposits of valuable Skyfire Gold and rare minerals.

The important design choice is that these hazards are not simply debuffs players endure until reaching the loot chest. Each phenomenon creates resources required somewhere else in the progression system. Dangerous weather is simultaneously punishment and opportunity.

Going underwater turns oxygen into another survival resource

The other half of the map sits beneath the surface. Underwater ruins, shipwrecks, coral deposits and laboratories form an entire exploration layer, with progressively deeper areas increasing both contamination and the danger posed by marine life.

Players initially gain access to a Basic Diving Suit before upgrading toward the Shark Diving Suit, which offers stronger contamination resistance and increased swimming speed. Fish Oil Paste can provide additional temporary environmental protection, while Oxygen Tanks automatically activate when a player's normal air supply is depleted.

Other tools are considerably more situational. An Inflatable Float provides an emergency route back toward the surface, Air Cushions create temporary platforms on the water and the Spear Gun provides a dedicated answer when something hostile finds the player underwater.

Exploration itself is deliberately signposted through the environment. Glowing algae near the surface can indicate submerged laboratories, while treasure maps obtained from beachcombing, fishing, quests and settlement exploration can lead players toward underwater caches. The progression starts around shallow wrecks and gradually pushes toward deeper contaminated ruins once the player's equipment is capable of bringing them back alive.

That last part is crucial. Finding treasure at the bottom is only half of an underwater expedition. Once Human now also wants players thinking about the return journey.

Even the wildlife has started interfering with the ship

The ocean's fauna is not merely decorative. Giant Squid can attach themselves directly to vessels and immobilise them, forcing players to target and sever the tentacles before the creature retreats. Sharks continually track chosen targets, while Jellyfish periodically discharge electricity into anyone careless enough to swim nearby.

Some creatures become resources rather than straightforward enemies. Tuna can be hunted when they leap above the surface, while Bubble Fish create oxygen-restoring bubbles useful during long dives. Anglerfish provide an even stranger interaction: approaching their glowing lure grants temporary protection from seawater contamination, turning one of the deep sea's more unsettling inhabitants into an improvised sanctuary.

Bay Crocodiles can even be captured, bred and eventually ridden across the water. Their enormous size prevents conventional jumping, but mounted crocodiles provide damage reduction to themselves and their rider, with that resistance becoming significantly stronger in water.

It is exactly the sort of bizarre survival mechanic Once Human tends to excel at. Another game might give players a faster boat.

Once Human gives them a crocodile.

The lighthouses are warnings, not safe harbours

The trailers have repeatedly made a point of lighthouses, which would normally represent safety and navigation at sea. In Isles of Abyss, Starry Studio has deliberately inverted that expectation. Malla's survival rules warn of predatory lighthouses and other apparently familiar pieces of the ocean environment that cannot be trusted, including islands that may not be quite as inert as they first appear.

The new Gameplay Trailer doubles down on that language by challenging players to “take on the lighthouses,” although Starry Studio's detailed pre-launch Dev Blog has not yet provided the same mechanical breakdown for lighthouse encounters that it has published for Calamity Towers, Voyagers or the Sunken Lord. Their precise live behaviour is therefore something best confirmed once the scenario launches rather than extrapolated from trailer footage.

What is already clear is the design philosophy. Isles of Abyss wants navigation itself to become suspicious. A distant light may not mean safety, and an island worth approaching may be hiding considerably more than resources.

That idea also ties directly into the scenario's story. Experienced captain Malla, who rescues the player after a shipwreck, can sense the memories of the drowned through what the game calls communion with the deep. Together with Ran, she guides players through nautical journals, wreckage and submerged memories that gradually reveal what happened in these waters and why so many things seem connected to the same entity below them.

Calamity Towers turn your custom ship into raid equipment

The largest naval PvE encounters revolve around Calamity Towers, which scale from story-driven challenges into coordinated group battles and eventually an Abyss variant during Phase II. These fights are built specifically to test whether players have learned how to construct and operate their vessels rather than merely whether their personal weapon build is strong enough.

Tentacles create the central combat puzzle. Some block areas, others summon reinforcements, heal allies or share incoming damage, forcing crews to divide attention between support targets and exposed weak points. Certain defenses also receive structural protection, giving ship artillery a direct purpose beyond raw boss DPS.

The Phase II Abyss version layers additional hazards on top of those mechanics. Stronger tentacle combinations and aggressive cores are joined by Voyager reinforcements, while waves, heavy fog, icebergs and water tornadoes interfere with ship movement.

The scenario also includes Sea Calamity Zones, where a protected Calamity Hatchling sits inside naval mines, hostile turrets and shield infrastructure. Players can use artillery to destroy buildings, detonate mines before moving through them and collapse support structures holding defensive guns before finally breaking the shield around the central target.

It is naval combat being used as encounter design rather than simply placing health bars on enemy boats.

Voyagers turn ocean exploration into boarding combat

Not every naval fight takes place against an immobile structure. Voyagers patrol the ocean in multiple sizes and configurations, giving players enemy ships that need to be approached, disabled, boarded and looted.

Their characteristics vary. Some carry stronger weapons, different crew compositions or mine defenses, and their overall power increases as the scenario progresses. By Phase II, giant Voyagers can lead smaller ships in organised fleets, while additional vessels may unexpectedly enter an ongoing battle.

That boarding component is particularly important because it connects Once Human's familiar third-person combat with the new ship systems. Players are not sitting permanently behind cannons once they leave shore. A naval engagement can begin at range, transition into structural destruction and finish with players physically entering the enemy hold to search for valuables.

The ship therefore enables combat rather than replacing the game Once Human already was.

The Sunken Lord is something much larger than a sea monster

All of those systems ultimately point toward the Sunken Lord, the ancient presence Starry Studio has positioned at the centre of Isles of Abyss. The expansion's fiction suggests the sea itself is not simply a body of water but part of something much older and more hostile, feeding on memories and emotions trapped within the depths.

Its endgame encounter does not become available immediately. Isles of Abyss uses server-wide purification progress, and once that progress reaches 100%, the entrance to the Sunken Lord rises from beneath the ocean. Players first need to defeat a Calamity Hatchling and clear the entrance battle before descending farther toward the entity's Core.

The confrontation shifts away from open-water sailing and into corridors and multi-level platforms filled with coordinated tentacle defenses. The Core changes behaviour through the fight, combining barrages, violent physical attacks and spreading lava that gradually reduces safe space.

It provides the scenario with a communal objective rather than simply another private boss unlock. Individual players improve their ships and Tech, groups conquer progressively harder Calamity encounters and the wider server eventually reaches the point where everyone has opened the route toward whatever has been waiting underneath them.

Isles of Abyss completely changes the normal progression curve

The scenario also abandons traditional levelling as its main development system. Characters enter Isles of Abyss at maximum level, and advancement instead comes through Tech.

Exploration, resources and major challenges unlock new equipment rarity, ocean facilities and survival tools. Existing weapon and armour Blueprints can still be carried into the scenario, but the rarity players are allowed to craft and the number of active attributes on Mods are restricted by current Tech progress.

That provides a form of seasonal reset without making previously acquired collections meaningless. Veteran players keep their Blueprints and Mods, but cannot immediately deploy their complete endgame power on the first afternoon. The scenario gradually restores that strength while simultaneously asking players to develop an entirely separate naval infrastructure.

The Cradle system is disabled, reinforcing how deliberately Starry Studio has separated Isles of Abyss from the standard progression template.

Its roughly 21-day core cycle is divided into two phases. Phase I lasts approximately five to ten days depending on server purification speed, while Phase II lasts 11 days and introduces the deeper endgame challenges. A Permanent Server is expected to open on November 12 before the first group of normal scenario servers closes.

The free PvE scenario launches beside a much harsher PvP ocean

Players who like the ship systems but would prefer other humans to become the primary sea monsters also get Isles of Abyss: RaidZone. The separate PvP version uses the same oceanic foundation but removes much of the safety built into the standard PvE scenario.

There are no separate worlds inside its Naval Core Contest. Everyone competes across the same waters, resources are scarcer and encounters are deliberately more frequent. Island Survival asks players to establish supply lines and arm themselves quickly, while naval combat adds a genuine destruction economy to the vessels.

Ships have total HP, and attacks from other players can eventually sink them. Saved ship blueprints allow the vessel to be reconstructed, but supplies stored aboard a destroyed ship are not refunded. That turns the mobile-base fantasy into a far more dangerous proposition: packing the vessel with everything valuable makes expeditions convenient until another crew sends the entire inventory to the bottom.

The PvE scenario remains the headline version and the better fit for players primarily interested in exploration, storytelling and cooperative bosses, but launching RaidZone alongside it ensures the naval building systems are also tested under the pressure of human opponents.

This is much bigger than adding boats to Once Human

Isles of Abyss launches as a free Once Human expansion after maintenance on October 21 PT, corresponding to October 22 across much of the world, on PC, mobile, PlayStation 5 and Xbox Series X|S with cross-play and cross-progression. Starry Studio is also accompanying the release with login Blueprint rewards, a free commemorative weapon skin and Halloween activities.

The reason the expansion matters, however, is not the quantity of launch rewards. It is that nearly every major survival system has been altered to make the ocean meaningful. Base building becomes ship building. Environmental preparation depends on the island being visited. Fishing feeds production. Diving requires contamination and oxygen management. Ship artillery determines how certain bosses are approached. Exploration provides Tech, Tech improves the vessel and the improved vessel makes increasingly dangerous exploration possible.

That creates the kind of feedback loop a large survival expansion needs. The ocean is not an empty distance between interesting islands.

It is the new game space.

And judging by what is waiting beneath it, getting the ship into the water may be the easiest part of the voyage.