a.s.l.). Two more major springs are located in the river canyons bordering Arabika to the east: Goluboe Ozero in the Bzyb canyon (; a.s.l.) and Gega waterfall in the Gega canyon (; a.s.l.). There are also several smaller springs in the Gagra town. The Reprua River, one of the shortest rivers in the world, about long, starts in the cave and flows toward the Black Sea. Some boreholes located along the shore of the Black Sea yield karstic groundwater from depths of 40–280 m below sea level. Other much deeper boreholes tapped low-salinity karstic waters at depths of 500 and 1,750 m in the Khashupse Valley near Gantiadi and 2,250 m near Gagra. This suggests the existence of a deep karst system and vigorous karst groundwater circulation at depth. Submarine springs are known in the Arabika area, emerging from the floor of the Black Sea in front of the massif. Shallow springs at depths of 5–7 m can be reached by free dive near Gantiadi. Tamaz Kiknadze (1979) reported submarine springs near the eastern part of Gagra at depth of 25–30 m and Buachidze and Meliva (1967) revealed submarine discharge at depths up to −400 m by hydrochemical profiling. Recently an outstanding feature of the sea floor topography near Arabika has been revealed from a digital bathymetric map that combines depth soundings and high-resolution marine gravity data. This is a huge submarine depression in front of the Zhovekvara River mouth, which has dimensions of about 5 x 9 km and a maximum depth of about . The Arabika Submarine Depression is a closed feature with internal vertical relief of about (measured from its lowest rim) separated from the abyssal slope by the bar at a depth of about . It has steep northern and northeastern slopes (on the side of the massif) and gentle south and southwestern slopes. Its formation is apparently karstic. Presently this depression seems to be a focus of submarine discharge of the karst systems of Arabika. The speleological explorations and a series of dye tracing experiments conducted during the 1980s under the coordination of Alexander Klimchouk have radically changed previous notions of the hydrogeology of Arabika, revealed its outstanding speleological perspectives and strongly stimulated further efforts for exploration of deep caves. Tracers injected in the Kujbyshevskaja Cave and the Iljukhina System were detected in the Kholodnaja Rechka and Reprua springs, proving groundwater flow to the south-southwest