'Investigate the Tadpole Pens' walkthrough in Subnautica 2

To investigate the Tadpole Pens in Subnautica 2, you need a mysterious keycode. It would've been handy if the keycode was located at the Tadpole Pens ruins, but unfortunately, it's in an entirely different location, so don't waste your breath searching the wrong area. To get the keycode, you must venture into deep, heated underwater caverns — be sure to mind your water and oxygen levels.

Here's where to find the keycode needed to investigate the Tadpole Pens in Subnautica 2.

[Ed. note: Before you dive in, be sure to open the character menu and enable all landmark signals. This will make it easier to spot the locations mentioned in this guide.]

Update (June 8): Added more information on how to obtain a tadpole submarine ahead of this mission (optional), and what to do next.

How to investigate the Tadpole Pens in Subnautica 2

Shortly after finding the Wander Blackbox and curing the Angel Comb, you should get a Noetic Advisor alert named "tadpole pens." Listen to the alert to start the "Investigate the Tadpole Pens" mission. Before you head out, it's highly recommended to bring food, water, a few distraction flares, a fully charged scanner, and an air bladder. As this mission takes you deeper than ever before, there's a greater risk of drowning, so the air bladder's emergency oxygen can be a lifesaver. You must have equipped a basic air tank, but you don't need an advanced air tank or tadpole submarine for this mission.

That said, the mission becomes much easier if you do have a tadpole submarine at your disposal. Our guide on how to get a tadpole can help you out, but in short, you must scan three tadpole fragments (two of which are found at the Tadpole Pens, though some are closer to the Lifepod), obtain the moonpool blueprint, and place a vehicle fabricator at your base. This "Investigate the Tadpole Pens" walkthrough assumes you don't have a tadpole yet, so with or without a mini-submarine, you're ready to proceed.

Starting from the Lifepod, swim 690 meters east. You do not need to dive down until you're right above the signal. In the picture below (left side), you see the Tadpole Pens building in the distance, but be sure to aim for the oxygen tunic, the small blue plant that emits bubbles of oxygen, in the gorge opposite the building's entrance.

Graphic: Marloes Valentina Stella/Polygon | Source images: Unknown Worlds Entertainment/Krafton via Polygon

Touch the blue bubbles to replenish your oxygen, then enter the Tadpole Pens and head left to press the red button in the corridor.

Graphic: Marloes Valentina Stella/Polygon | Source images: Unknown Worlds Entertainment/Krafton via Polygon

Unfortunately, the door won't open as you need a keycode. Head back to the oxygen tunic outside before your oxygen runs out.

How to get the Tadpole Pens keycode in Subnautica 2

Feel free to explore the Tadpole Pens and start scanning, but know that the keycode isn't among the loot. A few minutes after pressing the red button, you will get another Noetic Advisor alert, which reveals the location of the Zip Blackbox. Interacting with this blackbox will get you the access key you need.

It's recommended to return to the Noetic Advisor (the nearest one available, which is probably the one in your Lifepod at this point) to listen to the message and obtain the Zip Blackbox signal, but if you don't want to swim all the way back, you can still follow this guide without it.

If you start from the Tadpole Pens, swim 210 meters to the southwest. Be sure to replenish your oxygen at the oxygen tunics along the path. See the circular alien device on the cliff's edge? Swim down, and pass through the large gap on the left (the one closest to the volcanic mound with the jellyfish ring). From there, take the tunnel to the southwest, leading into a large cavern with a large, fiery coral in the center.

Graphic: Marloes Valentina Stella/Polygon | Source images: Unknown Worlds Entertainment/Krafton via Polygon

If you start from the Lifepod, swim 350 meters southeast, passing Chap's Blackbox. At the edge of the cliff, swim down, use the oxygen tunic, then go down the large hole next to it. Feel free to explore the Hot Cave Basement at the bottom before moving on.

Graphic: Marloes Valentina Stella/Polygon | Source images: Unknown Worlds Entertainment/Krafton via Polygon

When you're ready, continue north-northeast and take the first tunnel on your right, leading into a large cavern with a large, fiery coral in the center.

Graphic: Marloes Valentina Stella/Polygon | Source images: Unknown Worlds Entertainment/Krafton via Polygon

No matter which route you took to get here, rest up at the oxygen tunic on the north-northeast side of this room. See the cave opening next to it? Swim all the way down to the bottom of this cave to find Zip's Blackbox. It's on the large purple root. Doing so will grant you the kurul level access key.

Graphic: Marloes Valentina Stella/Polygon | Source images: Unknown Worlds Entertainment/Krafton via Polygon

Now, return to the Tadpole Pens and press the red button again to complete the "Investigate the Tadpole Pens" mission in Subnautica 2. There's a room with breathable air and a Noetic Advisor behind the previously closed doorway.

So, what's next? Shortly after completing the "Investigate the Tadpole Pens" mission, you should receive the Alien Ruins signal, which will guide you to a brand-new region. If you haven't done so already, be sure to craft a tadpole submarine and stock up on base resources like titanium, copper, quartz, lead, and especially lithium, so you can set up a base when you arrive. As long as you bring a sonic resonator (and perhaps some spare batteries), you can farm every early-game resource around the Alien Ruins, except lithium, which is only found in the first area. You can replenish your lithium deposit more easily once you've set up a metal farm.

If you're starting out in Subnautica 2, we have a plethora of guides to help you navigate the deep blue sea. Our Subnautica 2 beginner's guide will set you off in the right direction and our base building tips will assist in planning out your sprawling base. Don't forget to stock up on food and water, too. (And if you want to get fancy with your food, you'll want salt!)

If you need help finding materials, we explain how to get the sonic resonator, which you'll want to mine tons of materials. We have guides on where to find these resources, like lead, sulfur, copper, quartz, and gold.

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