Tadpole Pens Guide: How to Open the Locked Door

A full walkthrough of the Tadpole Pens in Subnautica 2 -- how to reach it, where to find Zip's Blackbox keycode, how to open the locked door, and what to collect while you're there.

What You Need Before Visiting the Tadpole Pens

The Tadpole Pens sit deep within the Graveyards biome. Reaching the keycode requires traveling through the Hot Caves, a path that goes beyond what the Tadpole can safely handle without a Depth Module, so make sure you're well‑prepared before heading out.

Here are some items, vehicles, and tools that you might need:

Item	Why You Need It
Tadpole	Required to go into the hot caves.
Standard Air Tank	Increases O2 capacity to 75.
Rebreather	Slows oxygen consumption as you dive deeper. Pairs well with any upgraded Air Tank.
Distraction Flares	Optional since several hostile creatures patrol the area.
Air Bladder	Emergency supply of oxygen.
Food, Water, and Spare Batteries	This is a long trip, so bring extra supplies.

How to Reach the Tadpole Pens

The Tadpole Pens is approximately 680 meters east of the Lifepod at around 150 meters depth. Head due east past the coral gardens and into the graveyards region. You will pass another piece of Cicada wreckage along the way. The Tadpole Pens itself is just a little bit to the east and deeper. Look for a research station and ruined structures along the seabed.

How to Enter the Tadpole Pens

Enter the Tadpole Pens and turn left. You will find a closed door with a button in the corridor. Press it to start an authorization scan. The scan will turn red and your PDA will tell you a keycode is required. That keycode belongs to a colonist named Zip, and she took it down into the Hot Cave below the Tailings Village.

How to Get the Tadpole Pens Keycode

Exit the Tadpole Pens and head southwest through the canyon, about 210 meters from the Pens. You will enter Tailings Village, an area dotted with spherical structures. In the ground are three large holes leading into the Hot Caves below.

Step	What to Do
1	Drop through one of the holes in Tailings Village into the cave below. Head southwest through the entrance into the Hot Cave.
2	Follow the cave until it opens into a massive chamber with a giant thermal vent in the center.
3	Swim down the right side of the thermal vent and look for a hole in the rock leading further down.
4	Descend to the bottom of the cave. You are looking for an Angel Comb root at the lowest point.
5	Interact with Zip's Blackbox resting on top of the root. This adds the Kurul Level Access Code to your Databank. Don't forget to scan the Thermal Plant fragment near the blackbox.

Opening the Tadpole Pens Door

Retrace your route back out of the Hot Caves, past Tailings Village, and northeast to the Tadpole Pens. Head back to the door you tried earlier and press the button again. This time the scan turns green, and the door opens.

The first room has a few items to scan including a Repair Tool fragment, and a few pieces of alien ornaments such as Tall/Small Axum Jars, Wall lamp, and Coral Jar.

Next, head up the ladder, and you will find a NOA Terminal left behind by Sophie. Boot it up, exhaust the dialogue, and you will unlock your next objective.

All Items and Blueprints in the Tadpole Pens

Item	Where to Find It
Tadpole Fragment ×3	One on the cargo docks outside (beside the Power Transmitter fragment), one inside a cargo box in the first room, one in the backroom Moonpool.
Hydroelectric Turbine Fragment	Sitting outside the Tadpole Pens.
Halfround Room Recipe Data Card	On top of a table inside the Tadpole Pens' lounge.
Survivors Waypoint 2	On top of a crate before the locked door.
Moonpool Recipe Data Card	In the backroom near the parked Tadpole.
Scout Ray Chassis Fragment	In the backroom. Only requires one scan to unlock the blueprint.
Power Cell Terminal Fragment	Hanging on the left side of the wall in the backroom.

The Tadpole Pens are loaded with useful pickups. Do not leave without scanning for these fragments and collecting recipe data cards.

Related Articles

Recommended Guides

Walkthrough (Early to Late-Game)	Plant Farming Guide	Cooking and Recipes Guide
Best Biomods	Best Tadpole Upgrades	Metal Farm Guide

Progression & Priorities
Early Game	Mid-Game	Endgame

Lists

All Leviathans	All Items List	Biomes & PoI List
Blackbox List	Recipe Data Cards (Blueprints)	Vehicle List
Buildings & Facilities List	Best Base Locations	Best Tools to Craft

Notable Items

Salt	Silver	Copper
Lead	Lucifer Rotsac	Conduit Crystals
Creature Enamel	Enameled Glass	Troilite
Celestine

Guides for Beginners

Multiplayer Guide	How to Eat Food (Digestion)	How to Craft Items
Drinking Water Guide	How to Craft Air Tank?	How to Get Basic Fins
Scanner Station Guide	How to Manage Your Oxygen?	Base Guide
Alien Ruins	How to Use Coordinates	Tadpole Guide
How to Get More Storage	How to Get a Rebreather	Bioscanner Guide
Night Survival Guide	How to Heal	Angel Comb Guide
How to Power Your Base	How to Recharge Batteries and Tools	How to Get the Repair Tool
World Tree Guide	Flashlight Guide	Strong Acid Guide
How to Get Heat Tolerance	Scanner Guide	How to Get Tadpole Depth Module Mk. 2
How to Get a Wakemaker	How to Get Fibrous Pulp	How to Get a Wiring Kit
How to Get Advanced Wiring Kit	How to Get the Entangled Power Cell

Pre-Game Guides

Specs Requirements	New Game Features	Is There Crossplay?
Supported Devices	Update & Roadmap	How Long to Beat?
Can You Play Subnautica 2 on PS5 and PS4?	Is Subnautica 2 on Xbox?	Is Subnautica 2 on Steam?
Is Subnautica 2 on Switch?