Pupil control for better underwater vision NOV 20 2013
The Moken are a nomadic people who live on the coasts and islands of Thailand and Burma. They live off the bounty of the sea and have learned to control the size of the pupils in order to see better underwater.
Pupil constriction is triggered by incoming light levels -- the less light (as at depth) the bigger the pupil -- but the Moken have learned to override that implulse and keep their pupils small at low light levels, therefore making their eyesight sharper. (via the kid should see this)