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