Reef is a ridge (a long, narrow elevation of land) found near the surface of the ocean. Reefs are of two types, natural and artificial. Natural reefs are made up of plants, skeletons of small animals called corals, and other creatures of the water. Artificial reefs are man-made underwater structures built for the purpose of promoting marine life in areas of featureless bottom. There are several natural reefs, such as:
Live-bottom reef: It is a narrow horizontal surface of rock. Organisms such as sea anemones and seaweeds attach themselves directly to this rock, forming a live-bottom reef for fish and plants.
Oyster beds or shellfish reefs: These reefs consist of sea organisms named oysters (shelled sea animals). Oysters provide a hard surface, on which other organisms can grow. They provide protection for fish like gobies. These beds serve as a food source for animals like turtles. Oyster beds can be seen at low tide in the Chesapeake Bay in the United States.
Coral reef: One of the widespread reefs that contains 1/4th of the sea creatures and is home to billions of creatures.
