Shoal in the context of Tidal flats

A spit or sandspit is a deposition bar or beach landform off coasts or lake shores. It develops in places where re-entrance occurs, such as at a cove's headlands, by the process of longshore drift by longshore currents. The drift occurs because waves meet the beach at an oblique angle, moving sediment down the beach in a zigzag pattern. This is complemented by longshore currents, which further transport sediment through the water alongside the beach. These currents are caused by the same waves that cause the drift.

An isthmus (/ˈɪs(θ)məs/ ISS-məs, ISTH-məs; pl.: isthmuses or isthmi /-maɪ/ -⁠my; from Ancient Greek ἰσθμός isthmós 'neck') is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated. A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea counterpart of an isthmus, a narrow stretch of sea between two landmasses that connects two larger bodies of water.

A river island is any exposed landmass surrounded by river water. Properly defined, it excludes shoals between seasonally varying flows and may exclude semi-coastal islands in river deltas such as Marajó.

These islands result from changes in the course of a river. Such changes may be caused by interactions with a tributary, or by the opposing fluvial actions of deposition and/or erosion that form a natural cut and meander. Nascent vegetation-free shoals and mudflats may dissipate and shift or build up into such islands through deposition; the process may be assisted through artificial reinforcement or natural factors, such as reeds, palms, evergreen trees or willows, that act as obstacles or erosion barriers, so that water flows around them. Islands may be small or large, covering many square kilometers, examples of which are given below.

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.

A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave erosion planing down rock outcrops. However, reefs such as the coral reefs of tropical waters are formed by biotic (living) processes, dominated by corals and coralline algae. Artificial reefs, such as shipwrecks and other man-made underwater structures, may occur intentionally or as the result of an accident. These are sometimes designed to increase the physical complexity of featureless sand bottoms to attract a more diverse range of organisms. They provide shelter to various aquatic animals which help prevent extinction. Another reason reefs are put in place is for aquaculture, and fish farmers who are looking to improve their businesses sometimes invest in them. Reefs are often quite near to the surface, but not all definitions require this.

Earth's largest coral reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres (1,400 miles).

The South China Sea Islands consist of over 250 islands, atolls, cays, shoals, reefs, and seamounts in the South China Sea. The islands are mostly low and small and have few inhabitants. The islands and surrounding seas are subject to overlapping territorial claims by the countries bordering the South China Sea.

The South China Sea Islands constitute a distinct tropical moist broadleaf forest terrestrial ecoregion and the South China Sea Oceanic Islands marine ecoregion.

Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal flat ecosystems are as extensive globally as mangroves, covering at least 127,921 km (49,391 sq mi) of the Earth's surface. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries; they are also seen in freshwater lakes and salty lakes (or inland seas) alike, wherein many rivers and creeks end. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and aquatic animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily.

A recent global remote sensing analysis estimated that approximately 50% of the global extent of tidal flats occurs within eight countries (Indonesia, China, Australia, United States, Canada, India, Brazil, and Myanmar) and that 44% of the world's tidal flats occur within Asia (56,051 km or 21,641 sq mi). A 2022 analysis of tidal wetland losses and gains estimates that global tidal flats experienced losses of 7,000 km (2,700 sq mi) between 1999 and 2019, which were largely offset by global gains of 6,700 km (2,600 sq mi) over the same time period.

An ocean bank, sometimes referred to as a fishing bank or simply bank, is a part of the seabed that is shallow compared to its surrounding area, such as a shoal or the top of an underwater hill. Somewhat like continental slopes, ocean bank slopes can upwell as tidal and other flows intercept them, sometimes resulting in nutrient-rich currents. Because of this, some large banks, such as Dogger Bank and the Grand Banks of Newfoundland, are among the richest fishing grounds in the world.

There are some banks that were reported in the 19th century by navigators, such as Wachusett Reef, whose existence is doubtful.

Raja Ampat (Indonesian pronunciation: [ˌrad͡ʒa ˈ(ʔ)ampat̪̚]), or the Four Kings, is an archipelago located off of the northwest tip of Bird's Head Peninsula (on the island of New Guinea), Southwest Papua province, Indonesia. It comprises over 1,500 small islands, cays, and shoals around the four main islands of Misool, Salawati, Batanta, and Waigeo, and the smaller island of Kofiau.

The Raja Ampat archipelago is just south of the equator and forms part of the Coral Triangle, an area of Southeast Asian seas containing the richest marine biodiversity on earth. The Coral Triangle itself is an approximate area west-southwest of the Philippines, east-northeast and southeast of the island of Borneo, and north, east, and west of the island of New Guinea, including the seas in between. Thousands of species of marine organisms, from the tiniest cleaner shrimp and camouflaged pygmy seahorses to the majestic cetaceans and whale sharks, thrive in these waters.

Dogger Bank (Dutch: Doggersbank, German: Doggerbank, Danish: Doggerbanke) is a large sandbank in a shallow area of the North Sea about 100 kilometres (55 nautical miles) off the east coast of England.

During the last ice age, the bank was part of a large landmass connecting mainland Europe and the British Isles, now known as Doggerland. It has long been known by fishermen to be a productive fishing bank; it was named after the doggers, medieval Dutch fishing boats especially used for catching cod.

Marooning is the intentional act of abandoning someone in an uninhabited area, such as a desert island. The word is attested in 1699, and is derived from the term maroon, a word for a fugitive slave, which could be a corruption of Spanish cimarrón (rendered as "symeron" in 16th–17th century English), meaning a household animal (or slave) who has "run wild". Cimarrón in turn may be derived from the Taino word símaran (“wild”) (like a stray arrow), from símara (“arrow”).

The practice was a penalty for crewmen, or for captains at the hands of a crew in cases of mutiny. Generally, a marooned man was set on a deserted island, often no more than a sand bar at low tide. He would be given some food, a container of water, and a loaded pistol so he could die by suicide if he desired. The outcome of marooning was usually fatal, but survival was possible if the condemned could obtain a means of escape, as in the case of pirate Edward England.

Amanohashidate (天橋立; Japanese pronunciation: [aꜜ.ma no (|) ha.ɕi.da.te]) is one of Japan's three scenic views. The sandbar is located in Miyazu Bay in northern Kyoto Prefecture. It forms part of the Tango-Amanohashidate-Ōeyama Quasi-National Park.

This is a list of islands of Malaysia. According to the Department of Survey and Mapping, Malaysia, there are 879 islands in the country. The state of Sabah has the most islands with 395 islands within its waters. Apart from that, Malaysia also has 510 offshore geographical features which include rocks, sandbanks and ridges. In 2015, it was reported that Malaysia still has over 535 unnamed islands, prompting the need for the government to take quick action to prevent neighbouring countries from taking over these islands. Most of the islands in the state of Sabah have been given a name, according to a statement from the State Land and Survey Department director.

The Zhongsha Islands is a Chinese term for a collection of two skerries, many entirely submerged banks, seamounts, and shoals in the South China Sea. There are no islands in the Macclesfield Bank, the main part of Zhongsha. The Scarborough Shoal, which consists of two skerries, is not contiguous with the Macclesfield Bank, but Chinese sources treat them as one chain of geographical features. The whole of the region is claimed by both the PRC and the ROC, and various bits of the eastern parts are claimed by the Philippines. No country has constant control of the whole region, and there are disputes, such as the Scarborough Shoal standoff.

The PRC claims to administer the area as Zhongsha Daojiao Town (Chinese: 中沙岛礁镇; pinyin: Zhōngshā Dǎojiāo Zhèn), a town under the Xisha District of the Sansha prefecture-level city in Hainan. It has one Village-level division, Zhongsha Daojiao Residential Community. However, the seat of this town and residential community is not within the Zhongsha Islets, but on Woody Island.

A foghorn or fog signal is a device that uses sound to warn vehicles of navigational hazards such as rocky coastlines, or boats of the presence of other vessels, in foggy conditions. The term is most often used in relation to marine transport. When visual navigation aids such as lighthouses are obscured, foghorns provide an audible warning of rock outcrops, shoals, headlands, or other dangers to shipping.

In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The original depositional layering is tilted, such tilting not being the result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, which are known as cross-strata.

Cross-bedding forms during deposition on the inclined surfaces of bedforms such as ripples and dunes; it indicates that the depositional environment contained a flowing medium (typically water or wind). Examples of these bedforms are ripples, dunes, antidunes, sand waves, hummocks, bars, and delta slopes. Environments in which water movement is fast enough and deep enough to develop large-scale bed forms fall into three natural groupings: rivers, tide-dominated coastal and marine settings.