An alternating, horizontal movement of water associated with the rise and fall of the tide, these movements being caused by gravitational forces due to the relative motions of Moon, Sun, and Earth. Offshore tidal currents tend to exhibit rotary patterns, while in areas near coasts the currents follow rectilinear paths and reverse periodically (ebb and flow currents). Tidal currents can often reach velocities of 2.5m/sec near shores.