It is not a surprise to anyone that Subnautica is a pretty well known game that has a lot of underwater caves. Some of the largest caves (Jellyshroom, Lost River and Lava) as well as the other biomes and islands have been mapped already. However, no one has made public plan and profile maps of smaller, but not less difficult caves (view from the top and from the side). Thus, I decided to map everything that was challenging for exploration and made it public on the official wiki[subnautica.fandom.com], but my edits were deleted for reasons like "not accurate, not respecting wiki standards", which contradicts the whole term of a "free" wikia, commercialized by a private company named Fandom Inc and moderated by people interested in fish photos and not knowledge... but I'm not here to discuss these topics, I'm here to share my work with you, selecting Steam as my platform of choice.

It is important to mention that it is intended to be a simple navigation assistance and not a complete guide featuring where you can make nice screenshots.

Now, fill up your tanks, put your mask and HELMET, charge your MULTIPLE LIGHT SOURCES, take your scooter and COMPASS, check your rebreather's scrubber and descend with me as deep as you can.

The legend for my maps:
Green circle - exterior/outside hole (sometimes entry/exit)
Red circle - lava/hot
Red line - cave boundaries/stalactites/stalagmites
Grey line - upper/lower level
Green line - another upper/lower level
Magenta line - surface/atmosphere area/structure OR underwater plants/bridges/connections
Blue circle - water level from surface
Grey circle - passage/hole between levels
O - entry/exit

Alright, let's begin with relatively simple caves and end with more complex.

In this zone we will be visiting not just one, but 2 caves.

The first one has 3 entrances, but one of them is lava geyser, so you should consider only 2.
We will start from the east large entrance, advance a bit until lava, then we can either go up and exit cave or continue to the west and after a bit of moving between some pillars, we can finally exit cave from the upside.

Difficulty level: wait a bit for geyser
Start entrance XY coordinates: 89 243
Plan map (XY view from above):

Profile map (XZ view from side):


Another cave with 3 entrances is not that far away and has nothing in particular to consider.
Start from south-west entrance, take whatever path you want, then continue north-east to exit or north-west to exit slightly less easier.

Difficulty level: squize a bit for exit
Start entrance XY coordinates: 215 582
Plan map (XY view from above):

Profile map (XZ view from side):

Right, I know that Blood Kelp is pretty huge and not very easy to navigate in the dark, but we are not going inside, we are interested in a (not so) small cave in this zone.

We start from north-east entry with 3 pillars, then go to the other side of the large pillar to go down and finally, do the opposite to exit, since this cave has only one entrance.

Difficulty level: make a circle and another one
Start entrance XY coordinates: -785 1317
Plan map (XY view from above):

Profile map (XZ view from side):

OK, here is where some real fun (or pain) begins.

This cave is pretty large, it has 2 levels, 2 lavas geysers and 5 entrances. So be prepared for some challenge.

We start from west big entry, go down a bit until the first intersection, then we can:

• go north up until a geyser and go up until second level, from which you can exit north up or south up
  
• go south-east until lava and then exit north-east up or south-west up

All this is much easier being said than done, of course.

Difficulty level: you will get hot, twice
Start entrance XY coordinates: 881 1365
Plan map (XY view from above):

Profile map (XZ view from side):

Mountain island is an interesting zone with some surface-level caves, but we will be interested more in the underwater one, which is quite complex, but not that big.

Start from west underwater entrance, advance until upper level (separated by a bridge-like structure), go up, take one of 2 tight paths north or east to go farther up until another level, go east until a big cavity, from which you can ascend to surface level. Once on the surface, go south, then west to exit surface cave.

Difficulty level: better go to a surface cave, really
Start entrance XY coordinates: 250 975
Plan map (XY view from above):

Profile map (XZ view from side):

If you still wish to continue than I'm impressed because, we are going to visit 2 caves in Bulb Zone.

Both are not far from the big lava rift, we will start from the one on top with 2 entries.

Start with the right south entry, advance then either exit from the second entry on the west, either continue north down and go back after few circles.

Difficulty level: still same circles
Start entrance XY coordinates: 1212 530
Plan map (XY view from above):

Profile map (XZ view from side):


If you though that it wasn't that difficult, you're right, but not be so confident for what awaits you beneath the first cave.

The only entrance is to the west, go down south until a small duplex level (grey), continue down east to the lower level, this will lead you to a pretty confusing space with another duplex level (grey), a small cavity and two routes which will both lead down to another cavity north, which then will lead west down with a small cavity and a path up to another cavity. The only thing left to do is to repeat everything backwards to exit. I said it wouldn't be easy, right?

Difficulty level: you better have a really good sense of direction and some spare tanks
Start entrance XY coordinates: 1212 530
Plan map (XY view from above):

Profile map (XZ view from side):

Well, if you're still here, there is another 2 caves.

Like in the previous case, the first is close to the second.
Start south-west, continue down, go up north east and exit.

Difficulty level: piece of cake
Start entrance XY coordinates: -1211 -834
Plan map (XY view from above):

Profile map (XZ view from side):


You're probably thinking that this cave is going to be really complex, but it's not. What makes it really difficult to navigate is its size.
Start from south, continue down to a space with 2 bridges and 3 holes, go down to the lower level, continue down west until a huge space, take one of the 3 exits west or go north and take a large exit there near a big bridge. Also, I forgot to mention that your visibility in this area will be close to zero.

Difficulty level: dark caves, prepare to drown edition
Start entrance XY coordinates: -1205 -835
Plan map (XY view from above):

Profile map (XZ view from side):

The last cave that we are going to visit is pretty extreme.

Start from east, following some holes in the main passage, go down, from here you can:

• go to the upper duplex level south with double entry
  
• go to another upper duplex level north with 2 holes
  
• go down to the lava
  
• go up and then down to lava

After the lava, the closest passage will be an up hole, which will lead to a space, following a down passage, then continue west and at the intersection either right or left, both will lead to a big room with a floating island. Take the hole on the west side from the island and go up, after entering a space with a lot of obstacles continue up, then enter to another room north, take any of 3 exits north-east. At this point you have done one of the most difficult caves in the game.

Difficulty level: psychopathy
Start entrance XY coordinates: 881 521
Plan map (XY view from above):

Profile map (XZ view from side):

That will be all for now. There are some other caves out there, but they are pretty small or just trivial and not that interesting to map.

Underwater cave mapping is a pretty challenging and really dangerous task. This computer game, even while having compass, doesn't provide accurate tools to make maps (but you can create a submarine out of air). So, I'm completely aware that my maps aren't accurate and contain errors, but it's still better to have a map than not, especially if you have both the plan and profile views, which is needed for 3D navigation. Also, the game lacks some basic cave diving equipment, like reels, without speaking of decompression sickness and all other stuff that can go wrong. But still, a game is a game, and this one is pretty good, in fact I liked it very much, especially cave environments, furthermore, I found it interesting and challenging enough, without being realistic.

I guess, my next stop will be Below Zero, until then, happy caving.