An ocean current is a continuous, directed movement of seawater generated by forces acting upon this mean flow, such as breaking waves, wind, the Coriolis effect, cabbeling, temperature and salinity differences, while tides are caused by the gravitational pull of the Sun and Moon.
RDDs - Radar Detector Detectors, All Acronyms, viewed April 15, 2017, <https://www.allacronyms.com/RDDS/Radar_Detector_Detectors>.
Radio direction finder. A radio direction finder (RDF) is a device for finding the direction, or bearing, to a radio source. The act of measuring the direction is known as radio direction finding or sometimes simply direction finding (DF).