Nature of currents.

Currents are permanent or seasonal horizontal movement of water flowing in a certain direction and in the oceans caused by differences in temperature, salinity, density and wind.  Information concerning their direction and strength is given on charts, in Sailing Directions and various current atlases.  The net result is a uniform movement of water in a given direction that transports a vessel bodily without affecting the ship’s head.

Nature of tidal streams.

Tidal streams are also horizontal movement of water but result from tidal forces and must not be confused with ocean currents although their immediate effect is the same.  Tidal streams can be rectilinear (flowing in two directions normally called ebb and flood) or rotary (continually changes direction through 360° in a complete cycle).  Information concerning  their direction and strength is given on charts, in Sailing Directions and special tidal stream atlases.