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