The Coriolis Effect

Wind Currents
The Wind Currents are put into gradual motion by the attraction of the Northern and Southern Celestial Systems, which are grinding against each other as gears at the equator line.

Water Currents
The rotation of small scale liquids in opposing hemispheres was debunked by Snopes.

As for water currents on a large scale; they're simply gradually put into motion by the winds. Water currents in the Northern Hemisphere will tend to rotate in one direction while currents in the Southern Hemisphere will tend to turn in another direction.