Subnautica 2 Guide: How to Get Tadpole Pens Keycode

The locked door inside the Tadpole Pens is Subnautica 2's first real puzzle that doesn't hold your hand. Your AI companion NoA eventually marks the objective, but if you try to reach it unprepared, the Hot Caves will end your run fast. This guide covers exactly where Zip's black box is, how to navigate the cave system, and what gear you need before you even think about dropping into that hole in the ocean floor.

What is the Tadpole Pens keycode and why do you need it?

When NoA sends you to investigate the Tadpole Pens, located roughly 675 meters east of the Lifepod in the lava vents area, you'll find a locked door blocking the main objective room. A recorded message from a colonist named Ganzo explains the situation: another Pioneer called Zip held the kuraltai access key, and she died somewhere beneath the facility. The keycode isn't a number you type in manually. Once you interact with Zip's black box, the data transfers automatically to your PDA and the door button becomes active.

Ganzo's message explains the key

What gear do you need before heading into the Hot Caves?

This trip is significantly longer and more dangerous than any previous black box run. You need the following before attempting it:

The Heat Tolerance Adaptation comes from clearing the Angel Comb located 200 meters northwest of the Lifepod at bearing 300 degrees, using the Sonic Resonator to destroy the viral flowers there. If you haven't done this yet, handle it before visiting the Tadpole Pens at all. For a full breakdown of building and upgrading your submarine, check out the Subnautica 2 Tadpole guide.

How to reach Zip's black box

Once NoA marks the location, here is the exact path:

1. Start at the Tadpole Pens entrance and travel southwest, keeping close to the ocean floor.
2. Head south at roughly bearing 195 degrees, through the ravine where lava pipes run overhead.
3. At approximately 540 meters from the Lifepod, you will hit a drop-off. Look for holes in the ocean floor and descend into one.
4. Follow the cave downward. Take the glowing blue tunnel entrance to the southwest as you descend.
5. At around 236 to 240 meters depth (approximately 475 meters from the Lifepod), you will reach a chamber with a large lava vent at its center.
6. Go down and to the right side of the lava vent chamber. There is a small cave opening here.
7. Exit your Tadpole Diver at this point. The passage ahead is too narrow for the vehicle, and going deeper will crush it.
8. Swim down to 310 meters depth. You will find a supply crate and two black boxes in this section.
9. The first black box near the top of the small cave belongs to another colonist. Zip's black box is at the bottom, resting on or near the supply crate, identifiable by the small human hologram marker above it.
10. Interact with Zip's black box. The keycode saves automatically to your PDA.

Cave entrance southwest of the Pens

What happens after you get the keycode?

With the data on your PDA, swim back up to your Tadpole Diver and return to the Tadpole Pens. Walk up to the locked door and press the button on the panel beside it. The door opens automatically.

Inside, you will find several scannable objects, including a Repair Tool blueprint. If you have not already unlocked the ability to repair your equipment, scan it here. There is also a ladder leading to a room containing a NoA unit. Interact with it and work through the dialogue to unlock a waypoint for the next story objective.

The Hot Cave itself is worth revisiting once the main objective is done. It contains resources, flora, and fauna to scan, and there is a Supply Crate near Zip's black box that you may have missed in the rush to grab the keycode.

For everything else happening in the game right now, the full Subnautica 2 guides collection has you covered from the very first steps to the deepest objectives.