A current meter is oceanographic device for flow measurement by mechanical (rotor current meter), tilt (Tilt Current Meter), acoustical (ADCP) or electrical means.
Current meters are usually deployed within an oceanographic mooring consisting of an anchor weight on the ground, a mooring line with the instrument(s) connected to it and a floating device to keep the mooring line more or less vertical. Like a kite in the wind, the actual shape of the mooring line will not be completely straight, but following a so-called (half-)catenary. Under the influence of water currents (and wind if the top buoy is above the sea surface) the shape of the mooring line can be determined and by this the actual depth of the instruments. If the currents are strong (above 0.1 m/s) and the mooring lines are long (more than 1 km), the instrument position may vary up to 50 m.