Here is the full list of all 17 Subnautica achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Repair the Aurora reactor
Hatch and release a Cuddlefish
Find the Degasi habitat in the deep grand reef
Find the Degasi habitat in the jellyshroom caves
Build a prawn suit
Build a seamoth
Create and deploy a time capsule
Launch the neptune rocket
Cure the infection
Find the Primary Containment Facility
Find the Enforcement Platform
Find the Thermal Plant
Find the Disease Research Facility
Build a habitat
Dive for the very first time
Find the Degasi habitat on the floating island
Build a cyclops