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