‘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.