A tribe of water nomads, the Mokens, living in Myanmar and Thailand  are able to see clearly underwater! The Moken tribe harvests tiny brown clams, etc. from the ocean floor from among brown stones without the aid of goggles.

Studies revealed that the Moken children’s vision is similar to European children’s vision on land but twice as clear underwater; the eye structure between the two groups is similar. The clear vision is attributed to the ability of the Moken children to voluntarily control accommodation while diving, effectively making up for some of the lost corneal power. It is believed, through preliminary studies, that this is ability is trainable.

Also, Moken children also constrict their pupils more (to 1.96 mm) than European children constrict (only to 2.5 mm) which may contribute to the sharper underwater vision. This is the same idea as using a smaller aperture on a camera to obtain a sharper image.