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