text: A current in a fluid is the magnitude and direction of flow within each portion of that fluid, such as a liquid or a gas.
  Types of fluid currents include:
  * Air current
  * Water current
  ** Current (hydrology), a current in a river or stream
  ** Ocean current
  *** Longshore current
  *** Boundary current
  *** Rip current
  *** Rip tide
  *** Subsurface currents
  **** Turbidity current
  *** Tidal current