Tadpole Pens and Zip's black box
The locked door at the Tadpole Pens is linked to Zip's black box in the Hot Caves. Reach the Pens in the eastern volcanic area, follow the cave route south of the facility, recover Zip's access information, then return to the door. This is a long dive with a final swimming section, so prepare Heat Tolerance, oxygen and vehicle power before leaving home.
Updated . Includes story-location spoilers.
Before following the Pens signal
| Bring or complete | Why it matters |
|---|---|
| Heat Tolerance | The eastern approach and Hot Caves are hot. Obtain the northwest Angel Comb adaptation first. |
| Tadpole, repair supplies and spare power | The trip extends well beyond the starter gathering loop. Leave with a repaired, powered vehicle. |
| Upgraded oxygen tank and Wakemaker | The final part of the published route is on foot outside the vehicle; leave enough air for the swim back. |
| Food, water, healing and spare tool batteries | Avoid turning the return trip into a second emergency after recovering the box. |
NOA provides an “Investigate Tadpole Pens” signal as you advance the black box storyline. If it has not appeared, return to a working NOA terminal, review your current black box objectives and finish the available conversations. Do not assume that discovering the building automatically completes the preceding objectives.
Find the facility, then the Hot Caves
The published approach places the Pens roughly 675 metres east of the Lifepod in the volcanic vents. Follow your active signal when available. Inspect the locked door and the information about Zip before leaving the facility; the cave detour supplies the missing access.
- Head south from the Pens, around 195 degrees. Follow the ravine beneath the overhead lava pipes until you find a cave entrance in the ground.
- Enter and look southwest for a blue-lit tunnel. Follow that passage downward. Keep track of this junction for the return journey.
- Find the chamber with a large central lava vent. Descend toward the right side and locate the smaller cave opening beside it.
- Park before exceeding your Tadpole's current crush depth. The published route leaves the vehicle here for the deeper passage. Refill oxygen before departing and establish the route back to your parked vehicle.
- Swim to the bottom of the cave ahead. Look for the large purple growth and the small human hologram marking Zip's black box. Recover the box and its access information.
- Retrace the route to the Pens. Return through the vent chamber and blue-lit passage, open the previously locked door, and complete the interactions inside.
If your remaining oxygen will not cover the same swim back, turn around before descending farther. A vehicle parked nearby is only useful if you can still reach it. Save mineral collection for a separate pass until you know the route.
Door and NOA troubleshooting
No Zip signal yet: the cave route can help you locate the box, but you can also return to NOA and advance the available dialogue for mission guidance. The bearings above are a route aid, not a replacement for checking your current objective.
You reached the hologram but the door remains locked: confirm you actually collected the black box and read the associated information, then return to the correct locked door at the Pens. Reaching a location alone does not recover its contents.
A terminal question differs from an older walkthrough: the Buddy System update corrected Question 6 in the Tadpole Pens dialogue. Follow the wording in your game. See the Buddy System update for the change.
Prepare for the next objective
Search the Pens for the Scout Ray Chassis blueprint before leaving. After investigating the facility, the next major journey crosses the gorge toward the Alien Ruins Research Station. Return to stock supplies and prepare a second base before making that crossing.
The caves also contain lithium, but a story recovery trip is easier with clear inventory space and an oxygen reserve. If vehicle power is your bottleneck, gather salt for Power Cells before departing.
Route reference
The landmark sequence follows PC Gamer's Tadpole Pens and Zip black box guide. Use your vehicle's current depth readout rather than treating an older vehicle configuration as your own limit.