The river is located in the northeast Primorsky territory of Russia. The northern and western boundaries of the river's watershed form the border between Primorsky territory and Khabarovsk territory. It confluences into the Sea of Japan at Samarga, a small town on the coast of the sea. In the estuary on the sea side, there is a kind of blind creek named the "Samrga duct" which extends for about 5 kilometres (3.1 mi).
Numerous small tributaries form a dense and extensive network in the watershed of the river.
The major left-hand tributaries of the Samarga River, facing downstream, are: the Perepadnaya River (30 kilometres (19 mi) long), the Dagdy River (70 kilometres (43 mi)), the Moi River (45 kilometres (28 mi)), the Isimi River (45 kilometres (28 mi)), and the Agzu River (30 kilometres (19 mi)). The Sobu, Zova, Dzolu, Kalashnikov, Takhalo, and Kipreinyi Rivers, among others, are minor tributaries.
The major right-hand tributaries are: the Pukhi River (60 kilometres (37 mi) long), the Kuksi River (30 kilometres (19 mi)), and the Bolshaya Sokhatka River (36 kilometres (22 mi)). The Bugu, Zaami, and Unity Rivers are minor tributaries.
The Samarga River’s average discharge is between 74 and 242 cubic metres (2,600 and 8,500 cu ft) per second. Its catchment area is around 7,760 square kilometres (3,000 sq mi). The length of the watershed boundary is 515 kilometres (320 mi). Floods are common in the summer and autumn.
The Samarga River watershed is so far the only place in the Primorsky territory with very high fish biodiversity and high natural fish productivity. The diversity of habitats provides for a wide variety of fish species.
A wide variety of fish, nearly 20 species –such as pink salmon, masu salmon, chum salmon, cherry salmon, Dolly Varden, white-spotted char, and grayling salmon – are abundant in the river and its tributaries. The river basin is also home to the largest population of a rare salmonid species – Sakhalin taimen. The Anadromous salmon (pink, masu, chum, and the less abundant coho) comprise a substantial part of the river biomass. The pink salmon stock is the largest, comprising 10% of the total population of pink salmon of the Russian mainland Sea of Japan coast. Masu salmon stocks rank second after pinks, and char are fairly abundant.
The production topography of the Samarga River is also very interesting. The lowest part of the river – from Unty Creek to the river mouth – is a zone of pink salmon, chum, rainbow smelt, and grayling salmon. The middle part of the river – from Zova Creek to Unty Creek – is an area of pink salmon, adult masu, taimen, lenok, and grayling salmon. The upper reaches of the river – upstream from Zova Creek – are home to juvenile masu, taimen, and grayling salmon.
The Samarga River basin is a unique ecosystem comprising many rare species of fora and fauna, including Japanese yew, ginseng, Amur tiger, Himalayan bear, Amur mountain goral, Gould’s merganser, and Blakiston's fish owl.
Rare plant species listed as endangered found in the Samarga watershed include: Japanese yew (Taxus cuspidata Siebold et Zucc. ex Endl.), woodland peony (Peonia obovata Maxim), ladyslippers (Cypripedium macranthon Sw., C. calceolus L., C. guttatum Sw.), two-rowed and candlestick lilies (Lilium distichum Nakai, L. pensylvanicum Ker-Gawl), Palibin’s edelweiss (Leontopodium palibinianum Beauv), and false juniper (Microbiota decussata Kom), among others.
The Samarga River basin is very rich in timber, metals, and hunting and fishing resources, but because it is in an extremely remote and mountainous region, with harsh climatic conditions, the accessibility and extraction of the natural resources in this river system is very poor.
There are currently four small towns in the area: Edinka, Peretychikha, Samarga and Agzu in the watersheds of the Edinka and Samarga Rivers. According to the 2001 Census, the total population in the riverine watersheds is about 800 people, representing various ethnic groups. Out of this number, 140 belong to the Udege people, an indigenous ethnic group. The present-day Udege population of the basin lives primarily in one village – Agzu – while the residents of the remaining three towns are largely of Slavic origin. Almost the entire people of the river system is actively involved in fishing – pink salmon and Dolly Vardena only.