Seven tenths of our planet is covered by water, and we live on the relatively small area of land that sticks up out of it. Keen divers will be seen venturing into almost any body of water where they are allowed.
If you lived on Mars and came to Earth for a diving holiday, Britain would probably not be your first choice of destination. The sea tends to be on the cold side, the visibility under water is less than we would like, and it is subject to strong tides. Yet every weekend during the diving season - especially along the south and west coasts - you will witness large numbers of divers venturing out to sea. Why
Britains cold and murky conditions are an attraction for divers - they create an irresistible sense of mystery and adventure. The British Sub-Aqua Club is a thriving institution with more than 50,000 members grouped in local branches, and they want to go diving. Add to that members of similar if smaller organisations such as the Sub-Aqua Association, the Scottish Sub-Aqua Club and Welsh Association of Sub-Aqua Clubs, and youll realise there are a lot of keen divers around.
So what do they see when they go diving Gales, fog, navigation errors and two world wars have dotted Britains coastal waters with a huge number of shipwrecks, and these form the bulk of our popular dive sites. Scapa Flow in the Orkneys, for instance, has one of the largest collections of war wrecks in the world. Wrecks are being rediscovered all the time and most sites are easily accessible by boat. There is something very exciting about swimming around the remains of a vessel lost at sea. Some would say it was something of a privilege.
Of course, scuba diving in the less-than-hospitable conditions found off Britains shores requires good training with the right techniques and equipment, and this is provided within the clubs or by diving schools.
After initial training in a swimming pool, instructors tend to take their trainees to the sheltered water provided by inland dive sites. There are a number of these flooded quarries, pits and lakes around the country.
To make the diving more interesting, the owners of these venues have positioned lots of wrecks in the water - of old cars, buses, planes, and even a helicopter or two. The diving can be so interesting that many divers have cultivated these places as their regular diving haunts.

A profusion of marine life like this will be found only in tropical waters.

Despite this, you probably would not catch a Martian diving in the UK. Nor would you find a high proportion of people who have taken up diving to experience the joy and comfort of the clear warm water found in many other parts of the world. For many, often those who have been trained by diving schools, diving is associated with holidays or specific trips to well-known diving destinations.
So for them, where is the best place to go diving
The Mediterranean is where it all started a little over 50 years ago with Jacques Cousteau and his rival Hans Hass, and today it is still the playground of Europe.
The Mediterranean is blessed with clear water, not always as warm as you would expect, but it has plenty of interesting sites. The western end, including the coasts of Spain, the Balearics, France, Corsica and Sardinia, has the most prolific marine life, a scattering of war wrecks and plenty of undersea caverns and grottoes.

Italy, Croatia, Greece, Turkey and Israel provide an opportunity to see submerged antiquities, but access is strictly controlled by the authorities. Perhaps the favourite diving islands for the Brits abroad are Malta, Gozo, and Cyprus.
As with most locations, diving can either be done from the shore, from small boats used on a daily basis, or from larger live-aboard vessels that spend longer at sea and can reach the more inaccessible sites.
Other places where diving is spectacular, if a little cold, include British Columbia with its giant octopus, California with its marvellous kelp forests, and the Mexican Sea of Cortez, where divers get a chance to share the water with Californian sea lions.

Meeting with a pufferfish in the Sea of Cortez, Mexico.

If you live in Britain, the nearest coral reef diving is found in the Red Sea off Egypt, Israel (Eilat) and Jordan. Egypts booming scuba diving tourist industry bears testimony to the popularity of diving with Europeans, and the cost of a trip there can be incredibly competitive.
This area of the world is not always hot; during the winter it can be quite chilly. However, the Red Sea is unique in having, not only a profusion of coral, but many varieties growing in close proximity. And there is a plethora of diveable shipwrecks dating from the Victorian era to the 1990s.
Other popular areas include Bermuda and the Bahamas, where the waters are warmed by the Gulf Stream. Bermuda, out in the Atlantic, is famed for its shipwrecks and the Bahamas, endowed with spectacular coral-reef walls and renowned for shark encounters, is a favourite underwater set for Hollywood movie-makers.
When you first learn to dive, probably the last thing you will want to see is a shark, but your perspective on these impressive underwater predators will change after your first sighting. You will not be surprised to learn that many divers pay handsomely for a chance to share the water with them.
Other areas to which divers flock if they want to see sharks close-up include the Galapagos islands of Darwin and Wolfe, and Cocos, a tiny island off the coast of Costa Rica.
Most areas of coral reef are found between the Tropics of Capricorn and Cancer. This includes the Caribbean area, the Indian Ocean and a large part of the Pacific.
The Caribbean is a favourite destination with divers from the USA, and normally dive operations in this area display the high level of efficiency and service on which their demanding American customers insist.
Bonaire and Curacao offer the easiest way to go Caribbean diving. Grenada and its sister island, Carriacou, offer healthy reefs and the Bianca C, one of the most spectacular shipwrecks in the world.
St Lucia is a romantic mountainous island with dive sites around two points called the Pitons. Here some of the original Superman film was made.
The Virgin Islands offer something for every diver, including the wreck of the Rhone (where Peter Benchleys film, The Deep, was shot), and either US or British culture, depending on the island you choose.
The Cayman Islands boast scuba diving as their biggest industry after off-shore banking, and are famous for over-friendly stingrays, while the Turks and Caicos islands offer snorkelling with whales at certain times of year.

A diver with one of the famously over-friendly stingrays of the Cayman Islands.

Florida provides the USA with its home-grown coral-reef diving, along with freshwater springs and several wrecks off Fort Lauderdale. Cuba forms the northern barrier of the Caribbean, and its reefs are becoming more popular with visiting European divers every year.
Mexico, with its Yucatan Peninsula, offers both reef and cavern diving, while Belize, with its strong British connections, has the second-largest barrier reef in the world.
The Maldives is a nation comprising a thousand tiny islands sprinkled across the Indian Ocean. Many islands are only a few centimetres above sea level and few can provide enough space for a hotel, yet they are second only to Egypt in their popularity with European divers.
Strong ocean currents feed the reefs among the atolls with nutrients, and all sorts of deep-water marine life is drawn in. Close encounters with giant manta rays are almost normal for divers here.

Kenya, bordered by the Indian Ocean, is earning a reputation for wildlife safaris below the surface as well as on land, and the paradise provided by the palm-fringed islands of the Seychelles hosts great tropical diving too.
We must not forget the Indian Ocean shore of South Africa with Sodwana Bay and Aliwal Shoals, both places where you will get to meet a raggie, the famous ragged-toothed shark.
The vast island nation of Indonesia, together with Malaysia, Borneo and Papua New Guinea, provides a wealth of tropical diving, and Australia offers the Great Barrier and Ningaloo reefs.
The latter is famous for guaranteed encounters with gentle whale sharks, the largest fish in the sea. Across in the Pacific, the thousands of islands that make up Melanesia, Micronesia, Polynesia and Hawaii dot the almost endless tracts of ocean. The wreck sites of the Solomon Islands and Truk Lagoon are legacies of the Pacific war; the wreck of the ss Coolidge waits in Vanuatu; Palau is famous for its wall diving; and Yap for its visiting giant manta rays.
The list goes on. Almost wherever there is water you will find divers. New Zealand has excellent marine reserves, and both South Africa and the southern coast of Australia have the great white shark, star of Jaws. Bolder divers pay to spend a dive inside a shark cage and experience the almost unimaginable. Finally, we should mention Japan. While not yet a popular holiday destination with European divers, this country has a huge coastline and its people have probably taken to scuba diving more than any other. One of their favourite training agencies BSAC (Japan), of course!