Passive biomods in Subnautica 2 are always-on perks like faster swimming near the seafloor, slower oxygen drain, base detection, and water filtering. The slot panel hints at six potential passive spots, which has led plenty of players to assume there's a hidden unlock chain involving the Bioscanner, biobed upgrades, or Adaptation Points. There isn't, at least not yet.
Why the slot is locked to one
The biomod menu shows multiple greyed-out passive slots, which strongly implies a progression path. The in-game databank confirms the cap directly, stating that only one passive biomod can be active at a time during Early Access. Scanning more fauna with the Bioscanner unlocks more passive biomods to choose from, but it does not expand how many you can wear simultaneously.
Things that do not increase the passive slot count in the current build:
- Unlocking every passive biomod via Bioscanner scans
- Building or upgrading Biobeds
- Completing adaptations (temperature, pressure, etc.)
- Crafting the Bioscanner itself
- Progressing into the second major biome zone
The active biomod panel behaves the same way in practice. While the UI suggests room for more, the equipped loadout is currently constrained, and swapping is done from the biomod menu rather than through expanded hotbar slots.
What you can do right now
Since you only get one passive equipped, the practical move is to unlock as many as possible and swap based on what you're doing. The Bioscanner is the gating tool for everything beyond the two defaults.
Step 1: Find the degraded Bioscanner inside a wreck in the second major area, roughly 1,800 meters east of the Lifepod (or about 600 meters southeast of the Alien Ruins signal). You'll need the Repair Tool to clear blocked vents on the way in.
Step 2: Scan the Bioscanner with your standard Scanner, then return to a Modification Station to craft the upgrade using 1 Scanner, 2 Enamelled Glass, and 3 Conduit Crystal.
Step 3: Use the Bioscanner on the specific fauna and flora tied to each passive biomod, then equip the one that fits the dive you're about to do.
Every passive biomod and its scan requirement
| Passive biomod | Effect | Scan requirement |
|---|---|---|
| Sea Skimmer | Swim faster near surfaces or the seafloor | Unlocked by default |
| Oxygen Control | Slower oxygen drain when stationary | Unlocked by default |
| Bioluminescence | Glow in the dark | Sandspear + Electric Geordie |
| Camouflage | Invisible to predators while stationary | Bullethead |
| Water Retention | More water gained from all sources | Coral Crab |
| Homing Sense | Detect nearby powered bases | Surge Jelly + Hammerhead |
| Threat Sense | Detect nearby threats via hair cells | Hoverthorn |
| Dermal Garden | Grow edible algae on your skin | Needler Mango |
| Slow Metabolism | Food meter drains slower | Nibbler Mango |
| Water Secretion | Slowly fills a water packet from seawater | Water Slug |
Loadout swapping suggestions
With a single slot, the smart approach is matching the biomod to the dive. Heading deep with no base nearby? Oxygen Control is the obvious pick. Exploring open water with predators around? Camouflage or Threat Sense. Long surface expedition between bases? Water Secretion or Slow Metabolism handles survival upkeep so you can stay out longer.
You can swap mid-dive from the biomod panel, so there's no penalty for changing your pick based on what's in front of you. Passive and active biomods occupy separate panels, so equipping one never blocks the other.
When more slots are coming
Unknown Worlds has flagged additional passive slots as part of the Early Access roadmap, but no specific patch date is currently confirmed. The studio has also said biomod names, counts, and unlock costs will keep shifting through Early Access, so the current single-slot limit is a development snapshot rather than the final design.
Until a patch raises the cap, the only meaningful upgrade you can make to your passive setup is unlocking more biomods to rotate through. Treat the slot as a build choice rather than a permanent loadout, and check the roadmap when patches land for the inevitable slot expansion.