Easter Eggs
Easter Eggs are hidden references to other games or pop culture.
Natural Selection 2
The Natural Selection 2 Poster can be found inside the Wreck in the Grassy Plateaus and placed inside your Seabase. There are many other objects from NS2 in Subnautica: Trello It is a reference to another game made by Unknown Worlds.
Portal 2
The first message broadcasted from the Communications Relay, which says: "This is an automated bounce back from the Aurora Mining Vessel. Your distress signal has been received. An emergency relief team will be dispatched to your location. *Static* Estimated arrival time: 9...9...9...9...9 hours". The wait time is a possible reference to Portal 2, whereas the announcer says to Chell (the protagonist): "You have been in suspension for nine...nine...nine...nine...nine..."
Holy Diver
A fifth message is received by the player's Communications Relay later in the game. The day this message is received varies. It displays: You've been down too long in the midnight sea. Oh don't you see what I mean? This message is a reference to the song Holy Diver by the US heavy metal band DIO.
Star Trek
The line occasionally said by the Data Terminal in the Precursor Ground-To-Air Weapon System "Resistance Is Futile", is a reference to the Borg from Star Trek.