Here is the full list of all 10 Dear Esther: Landmark Edition achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Uncover 4 urns
Trigger all voice over points
Drown Once
Finish Chapter 'The Beacon'
Trigger all director's commentary
Walk 5000 steps
Finish Chapter 'The Caves'
Finish Chapter 'The Buoy'
Die from falling off a cliff once
Finish Chapter 'The Lighthouse'