• 12 October 2026
• DancingCoder

We took the tunnel apart. The game finished the job.

At the end of Session 05, Session 06 was going to start with a shopping list. More Acidic Raion Pouches, a second Portable Oxygen Generator and a PDA for a locked room.

We did not go shopping.

We spent the whole session on a tunnel.

By the end of the night, it had taken us across the canyon to the Gateway Spire we previously had found. Getting there cost us one entire tunnel, all of the titanium inside it and, at the very end, all of our air.

Session 06 at a glance

• Players: DancingCoder and Mr.Pendragon
• Main objective: Take down BOTB's long tunnel and rebuild it aimed at the Gateway Spire, with Mr.Pendragon filming a timelapse
• Base expanded: BOTB, with a brand new tunnel, a few corners and a couple of extra rooms with windows
• Tunnels lost: One. About 300 metres of it, titanium included
• Key finds: A story PDA outside BOTB, a Blackbox and a note from Zip in a hot cave, and a strange structure in a new biome
• Still untested: The Dive Elevator
• Notable mishaps: A whole tunnel vanishing with one click, DancingCoder put outside the tunnel by a glitch, and both of us out of air at the very end
• Incidents resulting in a lost Tadpole: None. We did not have any
• Bases: Jenny and BOTB

The plan, and the timelapse

We found a Gateway Spire in Session 05. Getting to it was the problem. Every time we tried to swim across, the Collector Leviathan came for us. It does not like us.

So the plan was to take down our long tunnel, about 300 metres of it, and build it again at a new angle, aimed straight at the Gateway Spire we discovered previously. A more direct route over there, with walls around us the whole way.

Mr.Pendragon's job was to go outside and film the rebuild as a timelapse. It was just getting light, so he went looking for the right angle.

My job was to take the old tunnel apart. I walked to the far end to start.

It is a rather long tunnel.

Taking a tunnel apart is slower than building one

The first thing I learned is that you cannot deconstruct a room with something attached to it. We had put a light on the roof of the room at the far end, and the game would not let the room go until the light had.

Then my pockets filled up.

Deconstructing with full pockets puts whatever you cannot carry into one of those beacons that hold materials. My worry was that once the tunnel around it had gone, the beacon would drop into the water and we would never get it back.

So I ran back to empty my pockets.

There was nowhere to empty them. Our storage was full as well.

So I built a locker.

Outside, Mr.Pendragon had a problem of his own. The Portable Oxygen Generator could not make oxygen fast enough to keep him out there filming, and he had to head back to the base.

That was fine. The rebuild was the part we really wanted on film, and I was fairly sure building would be quicker than dismantling.

It is. Considerably.

Somewhere along the way, I heard the Collector Leviathan's music. Then Mr.Pendragon spotted it.

It knows. Of course it knows.

One piece of glass

With the room gone, all that was left at the far end was a beacon. I wanted it out before I took the rest of the tunnel down in one go, so it would not end up in the water.

So I went all the way back down the tunnel to fetch it.

It had one piece of glass in it.

We did not need any glass.

Then it was 200 metres back again.

I asked Mr.Pendragon whose idea it was to build a really long tunnel and then take it apart. He believed it was a collective idea.

I was glad I didn't get the blame.

Technically, a giant bug

Then something happened.

Neither of us was entirely sure what. Mr.Pendragon wanted to know whether he had just been launched upstairs.

The tunnel was gone.

All of it.

I had clicked dismantle once. The game told me it could not deconstruct it, and then the whole thing disappeared anyway. No beacon. No materials back. It had taken our tunnel and kept the titanium.

Mr.Pendragon blamed the Collector Leviathan. He said he would have to write it a letter, addressed to Mr. Collector Leviathan.

I like the fact that he keeps blaming the Leviathan. It was definitely just a bug.

"He's technically a giant bug," said Mr.Pendragon.

Fair point.

We were going to build a new tunnel anyway. We were just going to have to do it without the titanium from the old one.

Not a clean timelapse

The new tunnel started from a new room beside the one at the start of the base. I angled it slightly, checked with Mr.Pendragon that I looked like I was heading the right way, and started building.

He was back outside with the camera. It did not take long for both of us to agree that we were not getting a clean timelapse.

I had enough materials for about ten more sections. Or nine.

Then I ran out. I asked how far I had got. The game does not tell you.

Not very far at all.

We were going to need more titanium, because the bug had stitched us up. The logical answer was to build a locker, move everything out of one of our other rooms, and take that apart for its titanium as well.

It was never going to work in one go anyway. Mr.Pendragon suggested filming the second part from the other end, so I would be building towards him.

Right next to the red wall

While I was building, I had asked whether we were now heading into the Shiver Leviathan's area. If we were, we would end up with both Leviathans on our backs.

We found out soon enough. Mr.Pendragon was outside with the camera when we found the red boundary wall, right next to our new tunnel. The same wall the Shiver Leviathan guards, where I fed Mr.Pendragon to it in Session 04.

He swam to the end of the tunnel to work out where it was pointing. The angle was bad. Really bad.

So I went out to have a look for myself.

Add it to the body count

While I was looking, I ran out of air.

Mr.Pendragon had the Portable Oxygen Generator. It told me there was not enough stored.

I got a little bit out of it and raced back.

I was not going to make it.

I did not make it.

My revive countdown had 45 seconds left on it when I asked Mr.Pendragon to come and get me. He did.

Then I had to go and find the generator again, because I still had no air.

"Well, that was an epic failure," I said.

Mr.Pendragon added it to the body count. He also pointed out that I could have grabbed the other oxygen tank.

I did not even think of that.

Round a corner

Mr.Pendragon thought the next timelapse should probably be of something cooler than a tunnel. What we really need are the camera drones from the Scanner Room in the first Subnautica. Subnautica 2 does not have them. Unless it does later.

I asked whether the tunnel could just go straight through the out-of-bounds area, on the off chance the Shiver Leviathan would leave us alone. Mr.Pendragon did not think it would let us.

So, a corner.

A corner piece in this game is a right angle. That just seemed inefficient. Mr.Pendragon suggested a little S-bend.

Thrown out of the tunnel

Then the game threw me outside.

I had been in the tunnel, building the corner. Then I was in the water next to it. I had not built a hatch.

There was a shadow on the tunnel behind me, and it was not a human one. This is what I said at the time, it was clearly the Collector Leviathan.

Then it was gone.

Mr.Pendragon said it was like a bad horror picture.

I had a theory. The bug lost the tunnel, and now the bug was trying to kill me in the tunnel.

You can watch a clip of what happened to me on YouTube below.

He's guarding the Tadpoles

Through the window, Mr.Pendragon spotted the Collector Leviathan. It knew exactly where we were.

A bit later, it came straight towards the window. Mr.Pendragon reckons it is guarding the Tadpoles.

Both of which, as Session 05 established, are mine.

Interesting.

The middle of the canyon

We thought about going down for a look. As far as I can tell, ladders still only go up, so going down means building a room underneath and a ladder up into it. I was not going out there.

I was almost out of titanium again anyway.

Working out how far we had come was its own problem. The Tadpole Pens were 178 metres away, and the old tunnel had been 300 metres long, so we were not far enough yet. I should have put a beacon at the start of the base.

Mr.Pendragon went down instead. He came back up with titanium, and described the bottom as a big void of nothing. That is the middle of the canyon.

While he was down there, the Collector Leviathan passed right over him. He could see its shadow. I could not see it at all, and then I could. It was heading the other way. I told him to hurry up.

Mr.Pendragon's idea was to build the Dive Elevator there to get us down. Except that is only halfway across the canyon. The whole point of moving the tunnel was to get all the way to the Gateway Spire, and away from the Leviathan.

So the Dive Elevator stays untested. Again.

We would keep going a bit longer, then turn again so we did not go too far. Then Mr.Pendragon had to go, and we paused there.

You can view the full part 1 gameplay video of our session 06 below.

After a short pause

We came back after a short pause. Being fathers, we also have to play dad sometimes, not just games.

The tunnel did not get much further before the game told me I was not allowed to go that way. We had found the boundary again. 100% the boundary.

So, round another corner.

I was still really bugged out that the game had taken all the titanium from our old tunnel. We needed a room further on, and a room needs titanium.

Mr.Pendragon went out to see where we were, and I spent a while trying to spot him. The game really needs to make it easier to find your co-op partner.

Not that PDA

I went looking for titanium near the base, and for more of the brain-looking Acidic Raion Pouches. Instead, I found a PDA lying outside.

Not the one we need for the locked room.

It told us to go no further. Many before us had disappeared, and we were about to join them. It also said there was no need to go to the tree, because we would not find anything there.

It was just a story thing. A cheerful one.

There was no titanium near the base, either.

Lost in a hot cave

So I went further afield, and ended up right down in a cave. There was no titanium in there either.

Then I started burning up. In Session 03, it was Mr.Pendragon who went through the red vents in the Graveyard and announced that he was on fire. This time it was my turn.

I did not know where I was. I found lithium, which I did not want, and then loads of bubbles and some titanium, which I did.

Then I found a Blackbox.

Between the heat and the Blackbox, I think this is another part of the Graveyard. Mr.Pendragon reminded me that there are ten Blackboxes down there, and we have not found them all. I did not recognise this bit, though. The swim-through was definitely different to the one we did in Session 03.

Further in, I came up into an air pocket, and found a note from Zip. Zip had not found a way to eat the jelly yet, but reckoned the rings were "stuffed with heat shock proteins", and thought the cave was cooling down.

It was just a note. Not a missing PDA.

Then I had to get out, and I could not remember how I had got in.

I found the way out eventually. Then I saw Jenny's marker, which told me I was swimming in completely the wrong direction.

It's an important tunnel

Back at the tunnel, I built another room so I could see where we were. From there, I could see the other side of the canyon.

Four more sections and a hatch, and that was all the titanium. We were very close.

Mr.Pendragon could not see anything out of the windows apart from red water. It was dark again, so we were not going to brave it.

At this point, I apologised to anyone still sticking with us. How long were we going to spend on this tunnel?

"It's an important tunnel," said Mr.Pendragon.

A one-way trip

Mr.Pendragon went straight down from the tunnel. It is a long way down. I reckon the other side of the canyon is higher up, possibly another biome, and in between there is just nothing.

Then he ran out of oxygen.

This, he told me, was a one-way trip. For the cause.

It is technically a cheaty way of getting back to the base.

Salvage

Out of interest, I asked where our other Portable Oxygen Generator was. Mr.Pendragon had tried to get it. One of ours was in a cave. The other had glitched into the floor.

Titanium, it turns out, does respawn a little way outside the base. Mr.Pendragon had found some up on the ledges. I picked up some fish while I was out, because we were running low on food too.

It is very easy to lose your bearings at night. I headed for the cave without meaning to, and I was running out of oxygen again.

Mr.Pendragon spotted a bubble. "Go, Speed Racer, go."

I went a different way, and instead of heading into the cave, I came out behind it. Which meant I could fetch the Portable Oxygen Generator we had lost in there.

I found it, went back to the bubble for a breath and brought it home.

I had salvaged it. Unintentionally.

Mr.Pendragon, meanwhile, had got too close to a Marrowbreach, and it was trying to eat him.

On the way back, I found out you can pick things up while you are carrying the generator. I did not know that.

I came back with titanium, water, fish and some salt. With salt, we might get double food out of the fish, like we did in Session 05.

Mr.Pendragon had less luck with the pink, brain-looking things. Whatever they were, the game would not let him harvest them, with the tool or without it. He thinks there is a good chance he is just not smarter than his pickaxe.

Before he took the generator down to the far end of the tunnel, we checked its battery.

Empty.

BATTERIES, again.

I had the spare battery on me. Mr.Pendragon did not need it. He did mention that he may or may not be taking the oxygen tank for a ride, and promised to bring it back.

I asked him not to lose another one.

Right where we found it

Back to the tunnel. We had to be close now. Mr.Pendragon went out to look. We were.

I went out for a look myself, then got back in. I had advised Mr. Pendragon that I was going to remove the hatch and that he should come back inside, and he remarked What, you're not leaving me out here to die.

As if I would.

One more corner. Four more sections. A hatch.

And we popped out right where we had found the Gateway Spire. It was just there, on the other side of a rock.

We could not have made that more perfect.

"There it is," said Mr.Pendragon.

We needed an air bubble so we could stay longer. There were no bubbles.

That's mean, isn't it?

Something sticking out of the water

We went up a bit for a better look.

Mr.Pendragon found a building and told me to follow him. I was trying to take a breath from the generator he was carrying, and he kept moving.

Then I saw it properly.

"Look at this thing."

When I got close enough, I could see it was called an observatory. It goes all the way up and sticks right out of the water. We could not scan it.

I nearly did not make it to the top. Mr.Pendragon sorted me out.

"Thanks, sir."

Up there, I remembered the PDA. No need to go to the tree, it had said.

At the surface we could see the tree.

Mr.Pendragon thought that part of the observatory looked like a landing pad. There was a jet stream that went completely vertically up towards the surface. There were, as he put it, a lot of distractions.

I was trying to take in everything we were finding. I was also looking for a bubble, because without one we could not stay for long.

We found an entrance instead.

Was there air in there?

No.

I died first. Mr.Pendragon was not far behind.

You can watch the full part 2 gameplay video of our session 06 below.

What the tunnel taught us

A few things worth knowing if you are planning a tunnel of your own.

Take the attachments off before you deconstruct a room. A single light on the roof was enough to stop me from taking ours away.

Deconstructing fills your pockets fast, and whatever you cannot carry goes into a beacon. Have somewhere to put it all before you start. 

Building is a lot quicker than dismantling.

Corner pieces are right angles.

The game does not tell you how long your tunnel is. Put a beacon at the start, or measure against something you already know the distance to. We used the Tadpole Pens.

You can pick things up while you are carrying the Portable Oxygen Generator. Check its battery before you rely on it.

A successful session, eventually

For a session about one tunnel, Session 06 got a lot done.

We took the old tunnel apart, with some help from the game, built a new one at a new angle with a few corners to keep it off the red boundary wall, added rooms and windows, found a story PDA, a Blackbox and a note from Zip in a hot cave, salvaged a lost Portable Oxygen Generator and popped out right beside the Gateway Spire, next to a strange structure.

We also lost a whole tunnel's worth of titanium, did not get a clean timelapse, ran out of oxygen more than once and finished with both of us dead. I also got thrown out of a tunnel I was standing in.

I'd call that a successful session. Eventually.

Next time: Tadpoles

We need to get oxygen over there somehow, and the answer is a Tadpole. Building one at BOTB means a processor and a vehicle fabricator first. Building one at Jenny should be a lot easier.

So the plan is to go back, build Tadpoles and come back, with a moonpool at the far end of the new tunnel to bring them in.

Jenny is still about 900 metres away. In Session 05, I said the swim could wait. It turns out it could only wait one more session.

There is definitely something over there that we need to properly investigate. And somewhere, there is still a PDA for that locked room, more Acidic Raion Pouches to find and a Dive Elevator nobody has tried.

Session 01 taught us OXYGEN.

Session 03 taught us FOOD.

Session 05 added BATTERIES.

Session 06 was the resit. We still ran out of OXYGEN.

At least it's an important tunnel.