Unlike earlier diving, which relied either on breath-hold or on air pumped from the surface, scuba divers carry their own source of breathing gas, (usually compressed air), allowing them greater freedom of movement than with an air line. Both surface supplied and scuba diving allow divers to stay underwater significantly longer than with breath-holding techniques as used in free-diving.
A scuba diver usually moves around underwater by using swimfins attached to the feet, but external propulsion can be provided by a diver propulsion vehicle, or a sled pulled from the surface.
There are some underwater heavens for scuba diving have given bellow:
The Blue Hole
The Blue Hole is a large underwater sinkhole off the coast of Belize. This site was made famous by Jacques Cousteau who declared it one of the top ten scuba diving sites in the world. Recreational scuba divers are attracted to the crystal clear water and several species of fish that include giant groupers, nurse sharks and reef sharks such as the Caribbean reef shark and the Blacktip shark.
The Gilis in Indonesia has earned a reputation for being the 'turtle capital of the world'. Underwater holds some visual sights — an array of plant life and sea creatures such as green and hawksbill turtles, manta rays (rarely), bumphead parrotfish, black-tip and white tip reef sharks... plus countless varieties of hard and soft corals. Another plus, the island is cheaper than its neighbour Bali.
The only oceanic island in Malaysia, this place is teeming with life. Sipadan is surrounded by very rich reef life consisting of both hard and soft coral as well as all manner of reef fish — you will see cave systems, dolphins, bright coral... Sea turtles and white tip reef sharks can be seen on almost every dive and hammerhead and leopard sharks can also be seen at times.
Great Barrier Reef
The Great Barrier Reef needs no introduction. Expect all the tropical sea life here. Located off Australia, the world's longest reef has thirty species of whales, dolphins, and porpoises. On your diving expedition you may get to meet dwarf minke whale, Indo-Pacific humpback dolphin, and the humpback whale. Large populations of dugongs live there. Four hundred species of corals, both hard corals and soft corals are found on the reef.
Hawaii also offers some great scuba diving. The islands are ringed with reefs and wildlife. The area north of the islands has been made into the largest marine reserve in the United States ensuring great diving for years to come. So if you are planing Hawaii trip so you should have to take a limo rental as well.
Tropical islands as beautiful as Micronesia always have one thing in common: they are encircled by coral reefs. With a 90 mile coral lagoon, well over 1,000 types of fish, from barracuda to jelly to shark, the islands that comprise Palau in Micronesia are a splendid spot for scuba. It's out of the way, inexpensive, and pristine.
Waters of Costa Rica hold in them massive schools of fish. Start with the eagle rays at Punta Gorda and then venture off to Murcielagos Island and the Catalinas for a wealth of sea life. Here one gets the opportunity to see giant manta rays swimming alongside brightly colored tropical fish and sharks and gorgeous coral reefs.
Papua New Guinea
Once a secret gem for divers in Australia and the South Pacific at large, Papua New Guinea is now fair game as a prime scuba destination. No matter what your taste, from deep drops and shallow reefs, private lagoons and atolls and perhaps best of all, pristine wrecks — a contradiction but nonetheless — that harken back to World War II.
Galapagos Islands, Ecuador
The Galapagos Islands are much more than a hub of scientific discovery. Here scuba divers can mingle freely underwater with tortoises, penguins and a host of other wildlife. Catch all of them in action — sea lions, sting rays, golden rays, morays, marine iguanas, white tip reef sharks, whales, pelagic fish...
The Red Sea, Egypt
With a surfeit of endemic sea life, unique to the region, and loads of reefs with proprietary ecosystems, the Red Sea offers divergent scuba experiences. From Sharm El Sheikh to the wrecks at Sha'ab Abu Nuhas to the Thistlegorm and Ras Mohammed, you'll find excellent diving all over the Red Sea.