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.
Trigger all director's commentary
Uncover 4 urns
Drown Once
Trigger all voice over points
Die from falling off a cliff once
Walk 5000 steps
Finish Chapter 'The Beacon'
Finish Chapter 'The Caves'
Finish Chapter 'The Buoy'
Finish Chapter 'The Lighthouse'