The English Channel has a "megatidal" regime: in the Dover Strait, the tidal range varies between 3 and 9 m in neap-tide and spring-tide respectively. The tide currents are alternating and essentially parallel to the coast. Along the French coast, the fluvial supplies, distributed from the Bay of Seine to Cape Gris-Nez, generate a coastal water mass which drifts nearshore, separated from the open sea by a frontal area: this coastal flow is characterized by its freshness, turbidity, phytoplankton richness, and pollution content. Its width is only 3 to 5 miles, but because of the high concentrations of dissolved and suspended components, it is possible that the coastal flow plays an important role in the fluxes between the Eastern Channel and the North Sea.