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