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