Unlike land-based water reservoirs, there is no land submergence in the case of coastal reservoirs.^[3][4] They store water without disturbing land use by replacing standing salt water of the sea area by fresh water from a river.^[3] The coastal reservoir area is separated from the sea by building earth dikes, e.g. by dredging. Fresh water from these reservoirs can be used for irrigation, drinking water and industrial purposes. Sometimes the reservoirs are used for flood control and land reclamation. The social and environmental impacts of coastal reservoirs are often negligible compared to land-based water reservoirs.^[3] The construction costs are a few times less than the costs of land-based reservoirs since there is no expenditure for acquiring the vast land area, the submerged immovable properties and the rehabilitation of displaced people.^[3] The sea side of the coastal reservoir can also be used for locating a deep sea harbor.

It is technically and economically feasible to construct man-made freshwater coastal reservoirs up to 20 meters depth from the coastline. Excess water from the high rainfall regions needs to be collected in the coastal reservoir. The fresh water from a coastal reservoir can be used to irrigate coastal desert lands.^[5]

The following are proposed projects:

• The Reber plan involved damming the San Francisco Bay near the Golden Gate, in order to transform the San Francisco Bay into a giant freshwater reservoir that could be used to provide potable water and irrigation for the entire state of California.
• Yangtze River water can be fully harnessed by constructing a coastal reservoir on the left side of its river mouth to cultivate vast desert lands in northern China.^[6]
• Water transfer from the west central Africa (Congo River basin, Niger River etc.) to Northern Africa (Sahara desert) and South West Africa (Namibia and South Africa deserts)^[6]
• Water transfer from the south east Africa (Zambezi River basin, etc.) to North east Africa (Somalia, Kenya, Tanzania, etc.).
• Water transfer from the northern part of the South America continent from Venezuela, Colombia and Panama to desert lands of Chile and Peru by interconnecting Atrato and Tuira rivers to lift/transfer water from the side of Atlantic Ocean to the Pacific Ocean.
• Water transfer from Fly, Kikori, Purari, etc. rivers of the Papua New Guinea island to Northern Australia by blocking the shallow depth sea of Torres Strait between southern Papua New Guinea and Northern tip of Australia. For navigation purposes, a freshwater sea level navigation channel (20 m water depth and 500 m wide) is provided with locks at the entry to the sea to cross the coastal reservoir which is blocking the Torres Strait. The divided coastal reservoir into two parts is connected by underpass water tunnels for water transport.^[6]
• Water transfer from the north and south coastal areas of the western 'North America continent' to the southwestern region of the United States and central parts of Mexico.
• East to west Water transfer from a coastal reservoir on the Bay of Bengal sea to water deficit parts of India from Ganga and Bramhaputra flood waters.^[6]
• Water transfer from Andhra Pradesh state in India from Krishna and Godavari rivers flood waters to Tamil Nadu state in India with a coastal reservoir on Bay of Bengal sea.^[6]
• Water transfer from India and Sri Lanka to Pakistan and Iran with lengthy coastal reservoir on Arabian sea along the west coast of India from Rameshwaram to Strait of Hormuz.^[7]
• Coastal reservoirs with associated embankment canals can also be envisaged to cultivate most of the central Asian deserts by diverting water of Siberian rivers.^[6] Diversion of Siberian rivers water would enhance the Arctic seawater salinity above the salinity of Atlantic sea water which would facilitate more Atlantic seawater flow to mix with the Arctic seawater. It would trigger comfortable (not so cold) winters across Europe and Siberia.^[8]

A coastal reservoir project can also create adequate capacity Pumped-storage hydroelectricity potential to store the electricity generated by variable renewable energy sources and ensure adequate round-the-clock electricity supply.^[6] Due to irrigation, lands which are not available for cultivation and forestry can be turned into a habitat with copious greenery with enhanced carbon storage in the topsoil which would contribute in mitigating the global warming process. With the advent of cheap renewable energy like solar and wind power, the availability of energy sources is not an ongoing issue but water availability is still a major issue that can be solved by coastal reservoirs to a major extent.^[9]

• List of rivers by discharge
• List of largest unfragmented rivers
• Polavaram Project
• Pollution of the Ganges
• Water export