Taut wire systems can operate with a variety of switches or detectors that sense movement at each end of the tensioned wires.

Fish glide beautifully around each other, sensing movement and hardly ever colliding.

And a cataract growing over her left eye left her sensing movement only through sound and smell.

Some species also have lines of special sensitive cells running down their bodies, which sense movements and displacements of water, allowing them to swim in an orderly pattern.

It uses this phenomenal turn of speed to evade capture, sensing movements in the water from approaching hunters and then fleeing far faster than a seahorse could swim.