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