Oxygen Not Included has no page on this site, so this is the first read of its only 2026 expansion. The nearest colony-sim piece here is a Songs of Syx write-up on why food chains break at 500 citizens — throughput maths in a different game with a different simulation. What follows is narrower: what The Aquatic Planet Pack puts on the map according to Klei’s own store page and patch notes, what each addition does to the first twenty cycles, and which numbers those pages never state.
Everything below assumes game update 744825, published 28 July 2026 — the newest post on the game’s Steam announcement feed when it was read for this piece. Anything Klei has shipped since then is not reflected in these notes.
What this covers: The Aquatic Planet Pack’s documented contents — a flooded starter world, swimming as a skill, the latex-to-rubber chain and pool-based ranching — and the practical sequence they imply for a new colony. Why it matters: The pack costs $9.99 and changes the first hours more than the late game, so the decision is whether to start a fresh colony on Marinea or to keep a dry-land base and treat the pack as extra content. Who should care: Players who own the base game and are deciding on the pack, plus anyone restarting after the June 2026 free update who wants to know which habits no longer apply.
What Klei’s own list says is in the box
Two Klei pages give the contents, and they do not fully overlap. The store page groups the pack into a swimming skill, aquatic ranching, new elements, cosmetic blueprints and a recruitable “sole survivor”; the launch announcement names the world and its biomes.
| Piece | What the fetched pages state | What it changes in a fresh colony |
|---|---|---|
| Starting world | “New starting world: Marinea!” (launch post) | You begin flooded rather than on dry ground |
| Biomes | Beach, Reef, Kelp Forest, Abyss (launch post) | Four named regions to dig through instead of the base set |
| Movement | “Train your Duplicants to swim”; a Basic Swimming skill exists and Divemaster grants it | Traversal is a trained skill, not a default |
| Breath | A puffed-up fish Duplicants “can sneak a life-saving breath from” when drowning (store page); a Breathing Station building exists | Breath becomes a resource you can site a building around |
| Ranching | Expanded aquatic ranching, geysers and marine critters yielding “new foods, building materials, and even oxygen” (store page) | Food and oxygen chains get a second, wet input |
| Materials | Latex from pulverised palm wood into rubber at a new vulcaniser, giving rubber boots, 4kW insulated conductive wires and gaskets (pre-launch post) | A three-step industry gates insulated wiring and sealed buildings |
| Duplicants | Kai, and Minnow the recruitable survivor (launch post) | Two named colonists with distinct traits (see below) |
| Cosmetics | “More than 100 new cosmetic blueprints” in the Supply Closet (store page) | Costume only, no mechanical effect claimed |
Two dates are worth keeping straight. The store page and the appdetails record both put the release at 11 June 2026, and the pre-launch post promised “next Thursday, June 11th”. The 11 June announcement’s own FAQ then says the pack “launches on Steam, WeGame, and Epic today (June 12th)” — an inconsistency inside a single post, reproduced rather than smoothed over. The price is unambiguous: 9.99 USD, in both announcements and on the store page.
It does not need Spaced Out!, as both announcements answer flatly and the launch FAQ repeats. The base game is required.
Swimming is a skill line, not a movement upgrade
The pack’s headline is that Duplicants swim, and the patch notes show swimming is gated behind the skill system rather than switched on globally. Update 737195, one day after launch, fixed a specific case: Duplicants who start with the Divemaster skill now also get Basic Swimming, “even on non Marinea starts”. That sentence does two jobs: there is more than one swimming skill, and the system reaches colonies not on the new world.
Minnow carries the pack’s most legible stat line. Update 740622 changed two things about her: her Freediver trait “now provides +4 to all attributes while swimming”, and in new saves she joins with “+4 in all attributes and the Ancient Knowledge trait providing 3 Skill points”. That patch note is the reason to start a new save rather than resume a beta one.
Drowning is a real state with a recovery chain. The pre-launch post says Duplicants “have also learned how to perform CPR”, and the current patch notes still carry a rescue bug: incapacitated Duplicants were “teleporting to the bottom left of the world after being rescued and resuscitated” (744825). Update 737790 fixed a case where “swimming Duplicants struggle to find a safe area to recover breath”, and separately widened the Breathing Station’s description to cover “suffocating environments” generally rather than only liquid. Read together, those notes run from launch day to late July: the breath system was still being adjusted.
What no fetched page states: how long a Duplicant holds breath, how fast swimming movement is, or what the two skills cost in points. Plan skill points for swimming on a wet start; do not plan a number.
The rubber chain is the pack’s first real production line
The material loop is described most concretely, and it reads like a base-game chain with new nouns. The pre-launch post gives the order: pulverise the wood of an “otherworldly palm tree” to extract latex, then produce rubber “at the new vulcanizer building”. Rubber feeds three things — boots that “keep their tootsies dry”, “powerful 4kW insulated conductive wires”, and “the gaskets that many submersible buildings need”. The store page frames the same material as the route to “higher-voltage insulated wires and rubber boots”.
The gasket detail has teeth. The current patch notes fix a bug where “deconstructing buildings that have Gaskets now spawns a Gasket of the correct element, and not Genetic Ooze” (744825). That is a small line with a large implication: a gasket is made of a specific element and returns that element when you tear the building down. Before demolishing a submersible building for parts, check its gasket’s element: until late July the refund was the wrong material.
Do not assume the pack’s 4kW wires are the free update’s line item. The launch post lists “4k wires” among the base-game changes shipped to all owners the same day, alongside “flatulent Duplicants now producing bubbles when farting underwater” and “improved liquid visuals”; the pre-launch post credits the pack with “powerful 4kW insulated conductive wires”. Neither post says whether these are one feature or two.
The gaps matter more than usual here, because a production chain is where players expect ratios. No fetched page gives a wood-to-latex yield, a latex-to-rubber ratio, the vulcaniser’s power draw, or whether it needs heat input. Treat the vulcaniser as a building whose inputs you will discover in the database, and do not budget power for it from these pages.
Ranching under water works on pools, not rooms
The ranching rework is the section of the patch notes that changed most after launch, and the changes are mostly about what aquatic critters are not. Aquatic critters were being “groomed at the Grooming Station” (737790) — a bug, which tells you the dry-land grooming loop is not the aquatic route. Instead the pre-launch post names an Aquatic Milking Station that Seaquines are called over to for “the ingredients for Caviar”, and the notes add Fish Feeders and a Fish Pick-Up errand that “can now be made non-operational”.
The pool-versus-room distinction needs a careful read. Update 737790 says aquatic critters “will now reference pool size instead of room size in the Space Required section of their database entries, when describing Confined and Crowded conditions”, and that “the Field Guide has been updated to mention both pools and rooms”. That is a change to the database entry and the Field Guide — documentation catching up — not a statement that the simulation switched units. Build pools expecting confined and crowded to be pool-scoped, and expect the in-game text to say so.
| Name | What a fetched page states | Where it bites |
|---|---|---|
| Seaquine | Milked at the Aquatic Milking Station for caviar ingredients; “will now poop on a more regular basis” (740622); can “eat at Fish Feeders without falling” (737790) | Ranch layout: feeder height and floor placement |
| Beakon | “Blindingly bioluminescent” fish to swim alongside (pre-launch); “audio performance issue with Beakons” fixed (740622) | Audio cost, patched; no population figure given |
| Orehull | Description “now correctly says that its output is Polluted Mud” (737790); baby Orehulls “not flopping to water while watched because they are shy” (740622) | Byproduct handling and a flopping-movement fix |
| Blowter | Fixed “Blowters emitting bubbles into solid tiles and causing them to be destroyed” (740622) | Bubbles could destroy solid tiles |
| Slogo, Gildgo | Petta Pouf seed art changed so it is not mistaken for a critter egg; babies “no longer retaliate when attacked” (both 737790) | Beach-tier critters, safe to handle |
| Kelpole, Glo Squid | Kelpole harvest bug showed two Kelpoles (740622); Glo Squids “prowl the depths of the abyssal trenches” (pre-launch) | Deep-biome harvesting |
| Tidal Spring | “Fixed memory allocations of Tidal Spring” (744825) | Performance item, not a balance change |
One pool rule is unambiguous and mechanical: a fish “occupying a boundary cell of a pool will no longer be considered inside that pool” (740622). A ranch at the water’s edge therefore has a real boundary, not a free cell.
Food, and a quiet achievement change
The food chain connects to the base game’s progression in a way that is easy to miss. The current patch notes add “Nigiri and Sushi roll to the Carnivore achievement” (744825). If you are chasing Carnivore, the pack’s sushi output now counts toward it — a balance decision inside a line item that reads like housekeeping. The Sushi Bar also appears in the previous patch, whose notes list “Minor revisions to Sushi Bar animations” (737790).
Recipes, calorie values and cooking times are absent from every page fetched. The pack’s food identity, as documented, is new ingredients and one new preparation building; the arithmetic is not published.
What a dry-land colony gets from the same update
This part decides the purchase for most people, and splits in two. On 11 June every owner received a free update: the bubble and liquid-visual changes plus “4k wires” and, per the same post, a Klei Fest game update with “new buildings, bug fixes, and QOL”. The pack itself is separate and costs 9.99 USD; the store page’s system requirements repeat the base game’s list — Windows 10 version 21H1 or later, a dual-core 2 GHz CPU, 8 GB of RAM, Intel HD 4600, 3 GB of storage — with nothing extra added by the expansion.
The 28 July patch applies “all versions” fixes that have nothing to do with water: a “navgrid memory leak”, a “liquid rendering bug on older graphics cards”, optimised liquid texture array size, and a fix for empty-conduit request queuing. Those land whether or not you own the pack.
For an existing base, the notes answer the save question directly. The launch FAQ says you can “upgrade your old save” by opening the pause menu and clicking the DLC’s logo, which “will create a copy of the save with the DLC enabled”, and that in DLCs with new worldgen “those aspects will be available to new games only” — an upgraded base will not grow Marinea’s biomes into it. If the point is the flooded start, that is a new game; if the point is swimming and the material chain, the upgraded copy is the route. A “Previous Update Branch” exists for mods the free update breaks, and a “Scramble DLC” tool mixes owned DLC on a new game; Klei credits “long-time modder Aki, with whom we collaborated on parts of this DLC”.
Does a flooded start teach the loop, or hide it?
The base game’s own store page describes the loop as constant pressure from “scarcities of oxygen, warmth and sustenance”, with gas and liquid simulation, pipe systems, power grids and heat as the mechanisms you manage. Nothing in the pack’s pages replaces any of those; the pack adds a wetter input into each — plants that provide “even oxygen”, geysers, critters for food and materials, and rubber for insulated wiring.
So a Marinea start does not skip the loop. It relocates the first failure. On a dry start, the early question is where breathable gas goes; on Marinea the documented mechanics put a second question in front of it — how a Duplicant gets to the work, through water, on one breath, with a rescue chain behind them. That is an extra labour and skill cost before the familiar oxygen-and-heat management starts, and why the swimming skill and CPR chain appear so prominently in the fixes.
Whether the flooded start is easier on heat is the one question these pages cannot answer: no fetched page gives temperature values, heat capacity for the new liquids, or wattage for the new power options. If thermal headroom is your reason for buying, check the game’s database, not the patch notes. For the shape of that problem elsewhere, the Frostpunk 2 district heat guide runs the same adjacency logic in another game, and Timberborn’s floodgate automation is the closest read here to managing water on purpose.
What is still undocumented
Named so you can stop looking: no fetched page states swim speed, breath duration, the skill-point cost of the swimming skills, latex or rubber ratios, the vulcaniser’s power draw, critter diet values, temperature numbers for the new biomes, or morale effects for Kai and Minnow beyond the trait lines quoted. Nor does any page confirm whether the 4 June free beta is still accessible; Klei said it would be “playable right up until the DLC goes on sale”, which reads as closed.
The sequence the documentation supports is short. Start a new game for Marinea’s worldgen; put skill points into swimming before you need them; build the latex-to-rubber chain before planning a submersible building, because gaskets depend on it; site ranches by pool, not room, and keep critters away from the Grooming Station; then re-read the patch notes rather than a guide — this pack’s notes touched aquatic ranching in three separate patches after launch.