The Tadpole Pens keycode in Subnautica 2 is found by tracking down Zip’s Blackbox in the Hot Cave below the Tadpole Pens. The locked door inside the Tadpole Pens will not open from loot found in the building itself, so the real objective is to trigger the keycode step, follow the Zip Blackbox route, then return and press the red button again.

For more Subnautica 2 material routes, tool unlocks, and story progression help, use the main Subnautica 2 guide hub.

How To Get The Tadpole Pens Keycode In Subnautica 2

To get the Tadpole Pens keycode in Subnautica 2, press the red button by the locked door inside the Tadpole Pens, wait for the Noetic Advisor to reveal Zip’s Blackbox signal, then find Zip’s Blackbox in the Hot Cave southwest and below the Tadpole Pens.

The keycode is not sitting inside the Tadpole Pens as a normal pickup. That is the main trap with this objective. The locked door sends the player somewhere else, and the access key comes from Zip’s Blackbox in the heated cave system beneath the area.

Step	What To Do
1	Reach the Tadpole Pens after the Noetic Advisor alert appears.
2	Enter the Tadpole Pens and press the red button near the locked door.
3	Wait for the next Noetic Advisor alert tied to Zip’s Blackbox.
4	Go southwest and down into the Hot Cave below the Tadpole Pens.
5	Find Zip’s Blackbox near the purple root inside the smaller cave.
6	Return to the Tadpole Pens and press the red button again to open the door.

I would not waste time searching every corner of the Tadpole Pens for the keycode before doing the Blackbox step. The locked room is solved by leaving the building, not by staring harder at the same door. Classic ocean logic.

The video below shows the Tadpole Pens keycode route visually if the Hot Cave path is easier to follow with landmarks.

How To Start The Tadpole Pens Mission

The Tadpole Pens mission starts after progressing past Wander’s Blackbox and the Angel Comb objective, when the Noetic Advisor gives an alert called Tadpole Pens.

Listen to the alert to start the objective. The mission sends the player east toward the Tadpole Pens building, which sits in a hotter biome route than the early Lifepod area. Turn on landmark signals before heading out so the objective markers are easier to track.

The route is much safer with better oxygen and basic preparation. A basic air tank is required for the mission route, and extra emergency oxygen makes the cave section much less stressful. If early oxygen or material progression is still behind, the Subnautica 2 Silver guide helps with one of the first big air tank material walls.

Tadpole Pens Locked Door And Red Button

Inside the Tadpole Pens, head left in the corridor and press the red button near the locked security door.

The door will not open the first time. That is normal. Pressing the button helps push the objective forward and leads to the next Noetic Advisor alert that points toward Zip’s Blackbox. The keycode is connected to that Blackbox, not to a note or loose item inside the locked room.

Before leaving the Tadpole Pens, refill oxygen at the nearby Oxygen Tunic outside. The area can punish slow exploring, especially before better oxygen upgrades are crafted. Use the oxygen plants as route anchors instead of trying to freestyle the whole swim with one breath bar and good vibes.

Locked Door Detail	What It Means
Red button does not open the door at first	The keycode step has not been completed yet.
Keycode is not inside the Tadpole Pens	Zip’s Blackbox must be found in the Hot Cave.
Noetic Advisor alert appears after	The alert helps reveal the Zip Blackbox route.
Return after Blackbox	Press the red button again once the access key is obtained.

Zip Blackbox Location For The Tadpole Pens Keycode

Zip’s Blackbox is located in the Hot Cave below and southwest of the Tadpole Pens, inside a smaller cave near a large purple root.

This is the actual keycode location. The route drops into heated underwater caverns, then leads through a smaller opening inside the cave system. The correct Blackbox is not just any Blackbox nearby, so make sure the objective updates after interacting with it.

One route places the Blackbox about 210 meters southwest from the Tadpole Pens. Another route from the Lifepod sends the player southeast past Chap’s Blackbox and down into the Hot Cave route before continuing north northeast toward the correct cavern.

Zip Blackbox Detail	Info
Main area	Hot Cave below the Tadpole Pens
Route from Tadpole Pens	About 210 meters southwest, then down
Key landmark	Large cavern with fiery coral in the center
Exact search spot	Smaller cave near an Oxygen Tunic and large purple root
Reward	Kurul level access key for the Tadpole Pens door

Do not leave the area until Zip’s Blackbox has been found and the objective changes. Leaving early is the easiest way to swim all the way back to the Tadpole Pens and find out the door still has zero respect for the trip.

Route From The Tadpole Pens To Zip’s Blackbox

From the Tadpole Pens, swim about 210 meters southwest, descend into the cave system, then follow the route into the large Hot Cave chamber with fiery coral in the center.

Use Oxygen Tunics along the way to refill oxygen. The route has enough landmark support to be manageable, but it is still a deep mission path, so do not ignore every oxygen refill just because the marker looks close.

Route Step	What To Do
1	Leave the Tadpole Pens and swim southwest.
2	Use the Oxygen Tunics along the path.
3	Look for the circular alien device near the cliff edge.
4	Swim down through the large gap near the volcanic mound and jellyfish ring.
5	Take the southwest tunnel into the large fiery coral cavern.
6	Use the Oxygen Tunic on the north northeast side of the room.
7	Enter the nearby cave opening and descend to Zip’s Blackbox.

The biggest mistake on this route is treating the first big cavern like the final destination. The Blackbox is deeper, in the smaller cave connected to that room. Keep following the cave down until the purple root area appears.

Route From The Lifepod To Zip’s Blackbox

From the Lifepod, swim about 350 meters southeast, pass Chap’s Blackbox, descend at the cliff edge, then continue into the Hot Cave route that leads toward Zip’s Blackbox.

This route works if the Zip Blackbox signal is active or if the player does not want to start from the Tadpole Pens again. Use the Oxygen Tunic near the cliff drop, then go down through the large hole into the Hot Cave Basement.

From there, continue north northeast and take the first tunnel on the right. That leads into the large cavern with fiery coral in the center. Rest at the Oxygen Tunic on the north northeast side of the room, then enter the nearby smaller cave and swim down to Zip’s Blackbox.

Lifepod Route Step	What To Do
1	Start at the Lifepod and swim southeast.
2	Pass Chap’s Blackbox.
3	At the cliff edge, use the Oxygen Tunic.
4	Go down the large hole into the Hot Cave Basement.
5	Continue north northeast.
6	Take the first tunnel on the right.
7	Find the smaller cave by the Oxygen Tunic and descend to Zip’s Blackbox.

I prefer the Tadpole Pens route once the mission marker is active, but the Lifepod route is useful if the player reset back to base and wants a cleaner starting point.

What To Bring Before Looking For The Keycode

The best Tadpole Pens keycode setup includes food, water, a fully charged Scanner, distraction flares, an Air Bladder, and enough oxygen support for a deep cave route.

The mission can be done without turning the whole trip into an endgame loadout check, but the Hot Cave route is still more dangerous than early resource swimming. The air pockets and Oxygen Tunics help, but they are not a replacement for preparation.

Item	Why It Helps
Food and water	The mission route is long enough that basic survival can become annoying.
Scanner	Useful for scanning objects, fragments, and lifeforms along the route.
Air Bladder	Emergency oxygen can save a bad return swim.
Distraction flares	Helpful if hostile creatures make the route messy.
Basic Air Tank	Required for making the route manageable.

If the mission feels too tight because oxygen upgrades are behind, it is worth fixing that before forcing the keycode route. Subnautica 2 rarely rewards heroic underpreparation. It mostly rewards being slightly less doomed than last time.

What To Do After Getting The Tadpole Pens Keycode

After finding Zip’s Blackbox and getting the Tadpole Pens access key, return to the Tadpole Pens and press the red button beside the locked door again.

The door should open after the access key step is complete. Behind it is the objective room with breathable air and a Noetic Advisor, which lets the mission continue properly.

The Hot Cave is also worth revisiting later because it has resources, flora, fauna, and scan targets. If resource progression starts pointing toward rarer materials after this mission, the Subnautica 2 Lithium location guide covers another route connected to deeper exploration and hot cave progression.

Why The Tadpole Pens Door Will Not Open

If the Tadpole Pens door will not open, the Zip Blackbox step is probably incomplete, the red button was pressed before getting the access key, or the wrong Blackbox was found in the Hot Cave.

Problem	Likely Cause	Fix
Red button does nothing	The keycode has not been collected yet.	Find Zip’s Blackbox in the Hot Cave first.
No keycode in Tadpole Pens	The keycode is not in the building.	Leave the Tadpole Pens and follow the Blackbox route.
Zip Blackbox marker will not clear	The correct Blackbox may not have been interacted with.	Check the bottom of the smaller cave near the purple root.
Running out of oxygen	The route is too deep for careless swimming.	Use Oxygen Tunics, bring an Air Bladder, and return to safety before pushing farther.
Door still locked after returning	The access key step may not have completed.	Confirm Zip’s Blackbox was collected, then press the red button again.

The key detail is that this is not a typed code puzzle. It works more like an access key objective. Find the correct Blackbox, return to the locked door, and press the button again.

Final Blurb

The Tadpole Pens keycode in Subnautica 2 comes from Zip’s Blackbox in the Hot Cave below the Tadpole Pens. Press the red button by the locked door first, wait for the Noetic Advisor step, then travel southwest and down into the heated cave route to find the Blackbox near the purple root.

Once Zip’s Blackbox is collected, return to the Tadpole Pens and press the red button again to open the locked door. The keycode is not hidden in the Tadpole Pens itself, so searching that building forever is wasted oxygen with extra steps. Follow the cave route, grab the access key, and let the door finally stop being dramatic.

Featured