The Context - Artificial Human Sensors: Science and Applications - page 51

formation of images. This is a far-sighted behaviour indicating that focussing un-
der water at a point of light remains equally fuzzy at whatever distance it may be.
In order, to at least identify an object under water is probably to keep it as close
to the eyes, in order to get a large angle to the object. To make a comparison, a
coin in clear water becomes visible at an arm's length, however, a piece of iron
wire is invisible to detect under water at any distance. An additional problem is
also, that there is a substantial difficulty to estimate distances under water. These
experiments show that the humans are vulnerable, when entering and acting in
new and unexplored environment. The perception may be if less useful in these
prerequisites, as the habitat has in the long term been shaping our perception, in
order to get the best possible conditions to succeed in an unsecured but natural
habitat.
A personal test can, with advantages be conducted, to get the feeling of how
the world is explored from under the water. This experiment can indeed verify the
vision perception behaviour of the physical properties in the eye and lead to spe-
cific feeling of insufficient perceptual abilities. The light from the air has a quality,
when entering the water surface, that the light is changed when the ray makes an
angle smaller than 45 degrees with the vertical surface. This phenomenon will
result in a large disc above the head (which can be noticed if one is under the wa-
ter and looking up). If looking sideways (i.e., more than 45 degrees from vertical
line) the ray will be completely reflected at the surface and a mirrored image of the
ground will be seen.
Recent research indicates that the visual defect under water can be improved
by training and we able to see more clearly Gislen (2003). This can be seen in ocean
nomadic people in Southeast Asia who spend in an essential part of time under
water. However, children with an intensive underwater training can increase their
vision abilities under water, Gislen (2006). This study indicates the possibility to

Figure 2.12. The eyes of a fish. Photo courtesy and copyright Peter Wide c 2010.