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 landmarks
Gather all secrets
Finish the campaign
Visit all of the hotels
See all creatures
Gather all boat boosts
Climb to the highest point in the world
Visit the n/e/s/w boundaries
Stay in the boat for a complete Day/Night cycle
Use the postcard feature