Ship data collected in the 1960s and recent data from ship, aircraft and satellites indicate that the flow in the Strait of Gibraltar does not move in the form of continuous currents but as tidal-induced pulses. A descriptive model based on these data is presented. The model indicates that the pulses are a result of increases in the speed of the tidal streams as they encounter the constrictions of the regional bathymetry (especially the Camarinal Sill and between the Camarinal Sill and Tarifa). Periodic increases modify the regional flow so that during each tidal cycle, the eastward-flowing surface Atlantic water and westward-flowing deep Mediterranean water are alternately emitted as large pulses into the Mediterranean Sea (Atlantic water) and Atlantic Ocean (Mediterranean water).