Tonkovića spring, spring Majerovo (89m depth), and the source of Caves - the three largest and most copious sources of the river. Gacka river abounds in underwater caves and springs sites. The first study began in the second half of the 20th century, but until then, the underwater world Gacka was completely unknown. Majerovo richest source of the Caves, and lately his attention. It is believed that over half of underwater passages and channels Gacka still unexplored.