In this guide, you will come to know how to get the Blue Tablet in Subnautica. You have to follow the instructions carefully to get it.
Starting from the coral tube sticking up out of the water, you have to head about one bump or one and a half bump to the right of northeast until you reach a large drop with a large cave entrance in the bulb zone.
It is recommended to have a cyclops with an Mk2 depth module and sonar, a prawn suit with a Grapple arm, an Mk1 depth module, a sea glide. You will also need a high-capacity O2 tank, a reinforced dive suit, and a survival knife.
The main threats you will encounter in the inactive lava zone are the Sea Dragon Leviathan, you have to avoid them, and the lava lizard you can either avoid or kill using the stasis rifle and survival knife. You will also face a warper that can warp you out of your vehicle, so if it does, you can either run from it or deal enough damage to it, so it warps away.
There are also lava larva in the inactive lava zone; if you bring your cyclops down there, they will try to latch onto your cyclops and drain energy. You can use your knife to cut it off your vehicle.
The coordinates for this location are (1117, -268, 568).
You will also need at least one purple tablet to unlock the door to the blue tablet.
Here is the large drop and entrance you are looking for.
Once you’ve gone through the large entryway, you will need to continue heading down the entryway, and you will eventually come across a large hole in the ground. You have to go down in, and it will lead you to the inactive lava zone.
There is a ghost leviathan near the hole, so you have to keep your distance from it as you head down into the hole.
It is the large hole that you are looking for.
Once you are in the inactive lava zone, you wil see a large open area like this, you have to continue straight, and you will come across the lava castle in the center of the large area.
Once you’ve reached the lava castle, you will need to look around the sides of the castle for a small entrance with some green pillars and lights on it. And it will lead you inside of the lava castle.