Here is the full list of all 10 Submerged achievements. It takes around 4-5 hours to unlock all of the achievements on Windows.
Stay in the boat for a complete Day/Night cycle
Use the postcard feature
Climb to the highest point in the world
Gather all secrets
Visit all landmarks
Visit all of the hotels
Gather all boat boosts
See all creatures
Visit the n/e/s/w boundaries
Finish the campaign