Reef in the context of "Carbonate platform"

Tuvalu (/tuːˈvɑːluː/ too-VAH-loo) is an island country in the Polynesian sub-region of Oceania in the Pacific Ocean, about midway between Hawaii and Australia. It lies east-northeast of the Santa Cruz Islands (which belong to the Solomon Islands), northeast of Vanuatu, southeast of Nauru, south of Kiribati, west of Tokelau, northwest of Samoa and Wallis and Futuna, and north of Fiji.

Tuvalu is composed of three reef islands and six atolls spread out between the latitude of 5° and 10° south and between the longitude of 176° and 180°. They lie west of the International Date Line. The 2022 census determined that Tuvalu had a population of 10,643, making it the 194th most populous country, exceeding only Niue and the Vatican City in population. Tuvalu's total land area is 25.14 square kilometres (9.71 sq mi).

A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as a reef, a barrier island or islands, a barrier peninsula, or an isthmus. Lagoons are commonly divided into coastal lagoons (or barrier lagoons) and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world.

The Persian Gulf, sometimes called the Arabian Gulf, is a mediterranean sea in West Asia. The body of water is an extension of the Arabian Sea and the larger Indian Ocean located between Iran and the Arabian Peninsula. It is connected to the Gulf of Oman in the east by the Strait of Hormuz. The river delta of the Shatt al-Arab forms the northwest shoreline.

The Persian Gulf has many fishing grounds, extensive reefs (mostly rocky, but also coral), and abundant pearl oysters; however, its ecology has been damaged by industrialization and oil spills.

A strait is a water body connecting two seas or water basins. The surface water is, for the most part, at the same elevation on both sides and can flow through the strait in either direction, although the topography generally constricts the flow somewhat. In some straits, there is a dominant directional current. Most commonly, the strait is a narrow channel that lies between two land masses. Straits are loci for sediment accumulation, with sand-sized deposits usually occurring on the two strait exits, forming subaqueous fans or deltas. Some straits are not navigable because, for example, they are too narrow or too shallow, or due to the presence of a reef or archipelago.

An artificial island or man-made island is an island that has been constructed by humans rather than formed through natural processes. Other definitions may suggest that artificial islands are lands with the characteristics of human intervention in their formation process, while others argue that artificial islands are created by expanding existing islets, constructing on existing reefs, or amalgamating several islets together. Although constructing artificial islands is not a modern phenomenon, there is no definite legal definition of it. Artificial islands may vary in size from small islets reclaimed solely to support a single pillar of a building or structure to those that support entire communities and cities. Archaeologists argue that such islands were created as far back as the Neolithic era. Early artificial islands included floating structures in still waters or wooden or megalithic structures erected in shallow waters (e.g. crannógs and Nan Madol discussed below).

In modern times, artificial islands are usually formed by land reclamation, but some are formed by flooding of valleys resulting in the tops of former knolls getting isolated by water (e.g., Barro Colorado Island). There are several reasons for the construction of these islands, which include residential, industrial, commercial, structural (for bridge pylons) or strategic purposes. One of the world's largest artificial islands, René-Levasseur Island, was formed by the flooding of two adjacent reservoirs. Technological advancements have made it feasible to build artificial islands in waters as deep as 75 meters. The size of the waves and the structural integrity of the island play a crucial role in determining the maximum depth.

A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid for maritime pilots at sea or on inland waterways.

Lighthouses mark dangerous coastlines, hazardous shoals, reefs, rocks, and safe entries to harbors; they also assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and the advent of much cheaper, more sophisticated, and more effective electronic navigational systems.

The Territory of Ashmore and Cartier Islands is an uninhabited Australian external territory consisting of four low-lying tropical islands in two separate reefs (Ashmore and Cartier), as well as the 12-nautical-mile (22 km; 14 mi) territorial sea generated by the islands. The territory is located in the Indian Ocean situated on the edge of the continental shelf, about 320 km (199 mi) off the northwest coast of Australia and 144 km (89 mi) south of the Indonesian island of Rote.

Ashmore Reef is called Pulau Pasir by Indonesians and Nusa Solokaek in the Rotenese language. Both names have the meaning "sand island".

An islet (/ˈaɪlət/ EYE-lət) is generally a small island. Definitions vary and are not precise, but some suggest that an islet is a very small, often unnamed, island with little or no vegetation to support human habitation. It may be made of rock, sand and/or hard coral; may be permanent or tidal (i.e. surfaced reef or seamount); and may exist in the sea, lakes, rivers or any other sizeable bodies of water.

The Miskito Cays (Spanish: Cayos Miskitos) are an archipelago of small cays and reefs with an area of 27 km located off Mosquito Coast in the Caribbean exclusive economic zones of Honduras and Nicaragua. They are part of the Gracias a Dios Department in Honduras and the North Caribbean Coast Autonomous Region in Nicaragua. The Miskito Cays are composed of 76 formations that include estuaries, coral reefs, cays, seagrass beds, and islets, of which 12 of the formations are covered with vegetation and consequently form islands which are lined with white sand beaches.

In Nicaragua, the Miskito Cay (Cayo Miskito), also known as Cayo Mayor, is the largest and most important cay located in the center of the archipelago measuring 37 km. Other main islands are Maras Cay, Nasa Cay, and Morrison Denis Cay. The Miskito Cays Biological Reserve is one of 78 protected areas of Nicaragua, it was declared a protected area in 1991. The cays, along with a stretch of the adjacent mainland coast, have been designated an Important Bird Area (IBA) by BirdLife International.