Working out how to investigate the Tadpole Pens in Subnautica 2 is the game’s first proper puzzle, as you venture into the area’s Hot Caves to recover the door code that’ll let you inside. NOA doesn’t seem to send you to the Tadpole Pens until you’ve found the other black boxes, at least that’s how it was for me.
This is a significantly longer trip than finding any of the previous black boxes, so stock up on the usual water, food, batteries, health kits, and maybe bring a distraction flare just in case. All that said, here’s how to reach the Tadpole Pens, as well as the Zip black box location so you can open the door inside.
How to investigate the Tadpole Pens and open the door in Subnautica 2
Once you’ve got the quest to visit the Tadpole Pens from NOA, you’ll get a signal indicating “Investigate Tadpole Pens”, around 675 meters to the east of the Lifepod in the lava vents area. To get here, you’re going to need to unlock the Heat Tolerance Adaptation by clearing the Angel Comb 200 meters northwest of the Lifepod, bearing 300 degrees on the compass.
This requires the Sonic Resonator tool, which you use to destroy the viral flowers in the area, letting you claim the Adaptation as you did with the one to digest food. I’d also suggest upgrading your O2 tank and building a Tadpole, as well as a Wavemaker to swim faster.
When you arrive at the Tadpole Pens, you’ll find a door that you can’t unlock, discovering that a colonist called Zip took the door code down into the Hot Caves in the area. If you wait long enough, NOA will give you the Zip black box location as a mission, but that also means heading all the way back to your base. Instead, use the video above to find Zip’s black box.
If you can’t see the video, then you need to:
- Head south from the Tadpole Pens, on a bearing of about 195 degrees, through the ravine with all the lava pipes above until you spot a cave entrance in the ground
- Go inside and take the glowing blue tunnel entrance to the southwest, descending further in
- You’ll reach a chamber with a big lava vent in its centre—go down and to the right to discover a small cave entrance on its right side
- Exit your Tadpole here, as it’ll get crushed if you go any deeper, then swim down to the bottom of the cave ahead
- You’ll find Zip’s black box, and so the door code, on the big purple growth, so look for the little human hologram that indicates where it is
Once done, you can head back to the Tadpole Pens, open the door, and enjoy the surprise that waits within.
