Here is the full list of all 12 ABZU achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Perform a flip while riding a creature.
Ride the Great White Shark.
Witness predation while meditating.
Breach the water on the back of a blue whale.
Discover those that lurk in the abyss.
Discover the polar region.
Add all secret shells to your collection.
Complete the adventure.
Release fish from all the hidden pools.
Find all the meditation statues.
Leap from the water.
Burst 15 fish schools in the jetstream.