The “Investigate the Tadpole Pens” mission in Subnautica 2 stops you cold the moment you arrive. You swim nearly 690 meters east from your Lifepod, reach the facility, press the red button, and discover the door needs a keycode you do not have. The code is not inside the building. A colonist named Zip carried the kuraltai access key down into the Hot Cave below Tailings Village, and she never came back up. You need to retrieve her blackbox before you can progress.
This walkthrough covers how to trigger the mission, what gear to bring, two routes to Zip’s Blackbox, and how to complete the quest once you have the code.
How to Start the Mission
Shortly after finding the Wander Blackbox and curing the Angel Comb, your Noetic Advisor (NoA) sends an alert named “tadpole pens.” Listen to the alert in full to activate the mission marker.
If the alert has not fired yet, return to your Lifepod or base and wait. Continuing to explore and gather resources like Necrolei Cysts while you wait is a productive way to pass the time, since the trigger can fire while you are out in the field.
What to Bring Before You Go
This mission takes you deeper than any previous objective. The final swim to Zip’s Blackbox reaches around 310 meters depth, well below the comfort zone of your basic oxygen setup.
Required gear:
- Heat Tolerance Adaptation (mandatory for the hot biome)
- Basic air tank, fully charged
Strongly recommended:
- Air bladder for emergency oxygen on the final descent
- Food and water
- Distraction flares
- Fully charged scanner
- Tadpole vehicle (makes the deeper cave sections significantly safer)
To unlock the Heat Tolerance Adaptation, clear the Angel Comb located 200 meters northwest of the Lifepod. Use the Sonic Resonator to destroy the viral flowers and claim the Adaptation the same way you claimed your first one.
If you have not yet upgraded your equipment and still need materials to build the Tadpole or improve your oxygen setup, gathering Titanium Ingots before leaving is worth the extra time.
How to Reach the Tadpole Pens
From the Lifepod, swim 675 to 690 meters east. You do not need to dive deep until you are directly above the mission signal. The Tadpole Pens sit in the hot biome at roughly 150 meters depth.
Before entering, look for an oxygen tunic in the gorge opposite the building’s entrance. This small blue plant produces oxygen bubbles. Touch the bubbles to top off your tank, then swim inside.
Turn left at the entrance and head straight to the closed door. Press the red button in the corridor to start the authorization scan. The scanner turns red. Your PDA confirms a keycode is required. You cannot reach the NoA Terminal behind that door without it.
How to Get the Tadpole Pens Keycode in Subnautica 2
The Tadpole Pens keycode is not anywhere in the facility. A recorded message from Ganzo explains that Zip, a fellow Pioneer, held the kuraltai access key. She died somewhere beneath the Tadpole Pens. You need to find and interact with Zip’s Blackbox to receive the code.
The blackbox sits inside the Hot Cave below Tailings Village, roughly 300 meters from the Tadpole Pens at a depth of around 310 meters. Two routes get you there.
Route 1: From the Tadpole Pens (Recommended)
- Exit the Tadpole Pens and swim 210 meters to the southwest through the canyon.
- You enter Tailings Village, an area marked by scattered spherical structures.
- Look for four large holes in the seabed. These holes drop directly into the Hot Cave below. Swim down one of them.
- Head southwest through the entrance into the Hot Cave.
- The cave opens into a massive chamber with a large thermal vent burning at the center.
- Swim down to the right side of the thermal vent and look for a hole in the rock wall.
- Enter the hole and descend as deep as you can go.
Route 2: From the Lifepod (Alternate)
- Swim 350 meters southeast from the Lifepod. You will pass Chap’s Blackbox on the way.
- At the cliff edge, swim down and use the oxygen tunic you find there.
- Drop through the large hole directly next to the tunic.
- Continue north-northeast once inside and take the first tunnel on your right.
- This tunnel leads into the same large cavern with the fiery coral at the center.
Where to Find Zip’s Blackbox
Both routes converge in the same chamber. A giant thermal vent or fiery coral formation burns at the center of the room.
On the north-northeast side of the chamber, rest at the oxygen tunic before going further. The cave opening next to it drops straight down.
Swim to the bottom of this cave. At the very bottom, a massive purple Titan Rockbore root fills the space. Zip’s Blackbox rests on top of the root. Look for the small human hologram icon that marks the interactable point.
Interact with the Blackbox to receive the Kurul Level Access Code. The code saves to your Databank automatically.
Tip: Exit your Tadpole vehicle before descending past roughly 240 meters. The default Tadpole has a maximum depth of 250 meters and will be crushed if you take it deeper. Park it at the last safe depth and swim the final stretch.
Make sure you actually retrieve the Blackbox before leaving. If you exit the cave without interacting with it, the quest marker stays active and you have to make the full trip again.
How to Open the Tadpole Pens Door
Retrace your steps out of the Hot Cave and swim back northeast to the Tadpole Pens.
Turn left inside the entrance and walk to the closed door. Press the red button again. The scanner turns green this time. The door opens.
Inside, scan everything in the room. The Azum Jars scattered around the space are worth scanning, as is the Repair Tool. When you are done scanning, climb the ladder to reach the upper level.
How to Complete the Investigate Tadpole Pens Mission
At the top of the ladder is the NoA Terminal. Interact with it and boot it up. Work through every available dialogue option. The conversation is packed with lore about what happened on Proteus. Exhausting all the dialogue completes the “Investigate Tadpole Pens” mission and unlocks a waypoint to your next objective. Play Now!
