hydrotropism

Water molecules experience a slight attraction or repulsion depending on their orientation relative to one another. In a collection of molecules, the effect is neutralized due to overall randomized orientation; this is particularly true in the case of ice, where neighboring molecules are locked into configurations that cancel out the forces even on the smallest scale. Many organisms evolved the ability to align the water molecules inside their bodies, causing polarization in the water surrounding them. Over successive generations, this developed into a sense used to detect the speed, temperature, and mineral content of the surrounding ocean, and orient themselves relative to other organisms. Creatures that transitioned to a land-based existence tended to experience some atrophy of this sense as they relied more on sight and sound as long-distance sensory input, although hydrotropism remained useful in locating sources of clean water. The ability to manipulate water physically at a distance is currently only known to exist in humans.

Manifestation

As a non-visual sense, hydrotropism does not have a "look" except where a human is exerting effort on water.  Attempts to explain the sensation to those without it often involve describing it as a difference in thickness.

Localization

Hydrotropism is a 1/R² law.  The effect is naturally strongest in the ocean, where surface currents form effectively infinite planes of moving water and can be detected at full strength from the ocean floor.

Type

Natural