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