This photo of my photoalbum was taken in Okinawa.

Scuba diving is swimming underwater while using self-contained breathing equipment. By carrying a source of compressed air, the scuba diver is able to stay underwater longer than with the simple breath-holding techniques used in Snorkeling and Free-diving, and is not hindered by air-lines to a remote air source. The scuba diver typically swims underwater by using fins attached to the feet. However, some divers also move around with the assistance of a DPV (Diver Propulsion Vehicle), commonly referred to as a "scooter", or by using surface-tethered devices called sleds, which are pulled by a boat. The term SCUBA arose during World War II and originally referred to USA combat frogmen's oxygen rebreathers, developed by Dr. Christian Lambertsen for underwater warfare. Today, scuba typically usually refers to the in-line open-circuit equipment, developed by Emile Gagnan and Jacques-Yves Cousteau, in which compressed gas (usually air) is inhaled from a tank and then exhaled into the water. However, rebreathers (both semi-closed circuit and closed circuit) are also self-contained systems (as opposed to surface-supplied systems) and are therefore classified as scuba. Although the word 'SCUBA' is an acronym for "Self Contained Underwater Breathing Apparatus", it has also become acceptable to refer to scuba as 'scuba equipment' or 'scuba apparatus'.

Coral reefs are aragonite structures produced by living organisms, found in shallow, tropical marine waters with little to no nutrients in the water. High nutrient levels such as that found in runoff from agricultural areas can harm the reef by encouraging the growth of algae.[1] In most reefs, the predominant organisms are stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate (limestone). The accumulation of skeletal material, broken and piled up by wave action and bioeroders, produces a massive calcareous formation that supports the living corals and a great variety of other animal and plant life. Although corals are found both in temperate and tropical waters, reefs are formed only in a zone extending at most from 30°N to 30°S of the equator; the reef-forming corals do not grow at depths of over 30 m (100 ft) or where the water temperature falls below 16 °C (72 °F).