Imagine that you are swimming along in a huge school of fish. If every individual in it wants to suddenly turn right or left—and what's more, in dim light or even darkness—will you be able to avoid bumping into the other fish? Definitely not!
Yet such movements, impossible for us, are perfectly simple for fish, because they have been created with a perfect sensory system known as the lateral line. This system consists of dots or lines along both sides of the body, containing sensory cells in a channel under the skin. (John Downer, Supernature, p. 29.)
The lateral lines immediately identify the slightest change in outside pressure, water movement, or strength or direction of the current. In contrast to the sensory systems of land animals, fish use the water's pressure waves and its feature of transportation and reservation of chemicals. Through these sensory systems, fish can half-feel and half-hear vibrations. Thus they can determine the presence of a predator or obstacle before they actually see it, can locate their prey or predators and find their way among the water currents. In particular, their lateral line lets them detect low frequencies nearby—footsteps on the shore or bodies falling into the water—and react accordingly.
By the water's edge, you can speak, sing or listen to the radio, and not alarm the fish. Yet if you do anything to set the water in motion—for instance, if you rock a jetty or throw a stone into the water—all the fish around will immediately flee.
Nearby objects reflect the vibrations reaching them. In this way, when a wave lands on the shore, the returning vibrations reach the fish's body in a short time. The lateral lines in the fish's body analyze these time frames and from these vibrations, the fish is able to establish an image of its surroundings. The fish can acquire more information by swimming faster or creating more vibrations of its own.
The system works so well that the fish can perform very detailed scanning. For example, the Mexican blind cave fish depends entirely on its lateral lines. Although it has no eyes, it can perceive objects no larger than a pinhead in the darkness of the cave it inhabits.
In low visibility waters in particular, fish which swim in large schools in close proximity to one another use their lateral lines in order to detect rapid maneuvers.
These sense organs possess a most complex structure. Of course, it's impossible for such a sensory system to come about gradually and in stages, through random coincidences. In order for the fish to survive, it's also essential that the system emerge all at once. This is yet another indication that fish did not come into existence by evolving, as evolutionists would have us believe, but that they were created by God, flawlessly and with no elements lacking.
