To get a known fixed point to measure from, you need beacons, floating radio transmitters that stay stable in water.

Triangulation can be used for making maps in all sorts of ways, but the method we're going to use here is position resection: using three fixed, known points to determine your unknown location. That's why I prefer the second method, which fits better inside the tools of the game: Triangulation. Personally, I find pulling down a console menu a serious buzz-kill. If you really get stuck and you consult the wiki, you can use those coordinates to find whatever you've been looking for. If you find something cool or you're done exploring a certain sunken wreck, press F1 and note those coordinates so you can refer to them later. Under 'Camera world pos' you'll see three numbers shown as (x, y, z), where X is east-west, Y is depth, and Z is north-south. You can find coordinates by pressing F1 to bring down a console menu. Here's the first way: Everything in Subnautica has in-game coordinates. You can use whichever one you want, I'm not your dad. One of them is cool and fun and the other is dumb and boring. To actually note locations, you need a coordinate system, and you have two options: console coordinates or homebrewed beacon triangulation. If you want to keep track, make like it's a '90s-era adventure game and break out a notepad. When commenters or forum posters say they want a map in the game, they usually want a way to cross off explored areas or remember important locations. Since there's no in-game Subnautica map, you're going to need to take some notes yourself.

No crash powder in my subnautica game