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