what is coral ? Corals are marine invertebrates in the class Anthozoa of phylum Cnidaria. They typically live in compact colonies of many identical individual polyps. The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.
Underwater diving is the practice of descending below the water's surface to conduct underwater activities. In ambient pressure diving, the diver is exposed to the pressure of the surrounding water, and uses breathing apparatus for scuba diving or surface supplied diving, or when freediving, will breath-hold. The saturation diving technique reduces the risk of decompression sickness after long duration deep dives. Atmospheric diving suits may be used to isolate the diver from the effects of high ambient pressure. Although not usually considered to be diving, crewed submersibles can extend depth range, while remotely controlled or robotic diving machines can reduce the risk to human divers.
In biology, any group of fish that stay together for social reasons are shoaling, and if the group is swimming in the same direction in a coordinated manner, they are schooling In common usage, the terms are sometimes used rather loosely. About one quarter of fish species shoal all their lives, and about one half shoal for part of their lives.
A shipwreck is the remains of a ship that has wrecked, which are found either beached on land or sunken to the bottom of a body of water. Shipwrecking may be deliberate or accidental. UNESCO estimates that worldwide over 3 million shipwrecks, some thousands of years old, lie on seabeds
Coral reef fish are fish which live amongst or in close relation to coral reefs. Coral reefs form complex ecosystems with tremendous biodiversity. Among the myriad inhabitants, the fish stand out as colourful and interesting to watch. Hundreds of species can exist in a small area of a healthy reef, many of them hidden or well camouflaged. Reef fish have developed many ingenious specialisations adapted to survival on the reefs.