During recent years there has been a huge increase in the number of people taking part in the sport of scuba diving and as a direct result of this there has been an explosion in the number of people travelling abroad on scuba diving holidays.

Many holiday resorts nowadays have a dive centre where guests can "have a go" or even undertake a basic scuba training course. This is especially true of the many Egyptian Red Sea resorts where they take advantage of the easily accessible diving in the region

Most sports divers who travel abroad on diving holidays go on trips arranged through a specialist diving company.

There are dozens of companies in existence catering for diving trips all over the world.

This kind of trip is designed specifically for qualified divers or those intending to become qualified divers and the whole holiday centres around the diving activities.

It is vitally important that those intending to dive whilst abroad are properly trained in the use of scuba equipment and are familiar with the risks and dangers associated with the sport, i.e. basic resuscitation skills, recognition of the signs and symptoms of decompression illness and how to avoid it etc.

Qualifications can be obtained by joining a club prior to travel or attending a recognised diving school for training, and subsequently making sure that you keep your skills up to date.

Popular destinations with UK divers are the Red Sea, Mediterranean and Caribbean but other locations such as the Maldives, Great Barrier Reef, South East Asia and the Pacific Islands offer superb diving. The photograph leftshows the popular Red Sea resort of Sharm el Sheikh.

Diving holidays can either be land based at a resort or dive centre, or based aboard a specially designed dive boat known as a liveaboard.

It is important that all divers who are going on diving holidays are aware of the availability of (or lack of) hyperbaric facilities in the area they are visiting, or alternatively, how a diver may be evacuated to a chamber in the event of a decompression incident.

Decompression accidents can and do occur even amongst divers who use personal decompression computers.

Liveaboard divers can make up to five dives per day and are often most at risk due to the remoteness of their location.

Most reputable dive companies will operate dive boats that are fully seaworthy and are equipped with all the necessary safety and navigation equipment, and carry comprehensive first aid and oxygen equipment. (It is always worth checking). They should also employ fully trained and competent personnel as dive guides and boat crew.

All sports divers should make sure that their travel insurance includes cover for scuba diving. Divers must be covered for accidents which may occur during diving or as a direct result of diving, recompression costs, hospitalisation etc. and loss or damage to diving gear. The better dive companies will offer specialist diving insurance.

Divers should be able to provide proof of medical fitness should also take their 'C' Cards, Qualification Records or other evidence of their diving qualifications for the Dive Master or Guide to inspect.

If you are flying to your destination you will usually have a baggage allowance of 20kg plus hand luggage. This can be a problem since basic scuba gear weighs around 15Kg which does not allow for much else. If you also carry underwater photography equipment your allowance is quickly used up. For this reason, cylinders and weights are usually provided on site and equipment hire is also available. Sometimes divers get an extra 10Kg per person "sports allowance" Check with your agent.

Diving knives should always be packed with the rest of your diving gear and carried in the hold, never in your hand luggage. Pony bottles and emergency cylinders must be completely emptied and also carried in the hold.

Many divers travel abroad to dive on tropical coral reefs which are one of nature's wonders. Nearly all coral reefs are in the tropics which means that the local climate will be hot. Divers must take care to avoid dehydration and desist from sunbathing immediately following a dive since both are predisposing factors in decompression illness.

Most tropical dive locations are in and around developing countries with poor standards of hygiene etc. Therefore, all the usual travel precautions should be observed; i.e. vaccinations, malaria tablets etc.

Because of the repeated immersion in sea water, divers are prone to ear problems. Infections can result from sea water trapped inside the ear canal. Ears should be cleaned out with fresh water after the last dive of the day and dried without poking anything inside. Aluminium acetate ear drops are good for drying out the ears.

After several days diving a build up of mucus can lead to blockage of the sinuses and Eustachian tubes giving rise to problems during equalisation. Decongestants such as pseudoephedrine are useful for treating this condition. One tablet should be taken prior to the first dive of the day, the decongestant effect will last up to eight hours.

Dangerous Marine Creatures

Tropical waters can sometimes give the impression of being alive with dangerous creatures that can sting, bite, devour or otherwise injure the unwary diver. Divers intending to dive in the tropics should take time to familiarise themselves with the potentially dangerous creatures they will be likely to encounter to reduce the likelihood of injury from such creatures.

There is a general principle: if something is slow enough for you to catch it or touch it - DONT!

Everybody's favourite villain is the shark. However, most species of shark are completely harmless to man and even if a potentially dangerous species is encountered it will more often than not ignore the diver and swim away.

Most encounters with sharks are thrilling experiences but when they are encountered during a dive they should always be treated with the utmost respect and caution.

Coral Reefs

Coral reefs are underwater structures made from calcium carbonate secreted by corals.

Coral reefs are unique structures built up over many years. They flourish in the warm waters of the tropics, fringing islands and continents, and forming atolls far out in the ocean. Some are like beautiful gardens, paved with delicate corals and home to innumerable brightly coloured fish. Others are full of drama, with massive coral formations extending into deep water with sharks patrolling along the reef edge.

Corals are made up of millions of tiny sea creatures called polyps. Polyps are very closely related to the jellyfish and sea anemones and like the anemones they possess tentacles for catching their prey. They are colonial creatures with hundreds of polyps in a single coral colony and they co-exist with algae in a symbiotic union.

Each polyp secretes an exoskeleton of chalk which forms the basis of the reef and they are filter feeders catching tiny food particles with their tentacles. The algae is able to produce nutrients by photosynthesis and gives each coral its distinctive colour.

Coral reefs are almost exclusively located in tropical seas. This is because of the conditions required by the corals in order to sustain growth. Which are:-

• Bright sunlight - to enable photosynthesis.

• Warm water - optimal growth is between 24 - 32 deg.C

• Clear water - allows light penetration. Heavily silted water will choke the corals.

• Shallow seas - sunlight cannot penetrate sufficiently below 100 metres to allow reef growth.

Corals are normally found in marine waters containing few nutrients. Most coral reefs are built from hard, stony corals, and are formed by polyps that live together in groups. The polyps secrete a hard carbonate exoskeleton which provides support and protection for the body of each polyp. Reefs grow best in warm, shallow, clear, sunny and agitated waters.

Often called “rainforests of the sea”, coral reefs form some of the most diverse ecosystems on earth. They occupy less than 1% of the world ocean surface, about half the area of France, yet they provide a home for 25% of all marine species, including fishes, molluscs, echinoderms and sponges.

Paradoxically, coral reefs flourish even though they are surrounded by ocean waters that provide few nutrients.

They are most commonly found at shallow depths in tropical waters, particularly in the Pacific Ocean, but deep water and cold water corals exist on a much smaller scale.

Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection. The annual global economic value of coral reefs has been estimated at $30 billion. However, coral reefs are fragile ecosystems, partly because they are very sensitive to water temperature.

They are under threat from climate change, ocean acidification, blast fishing, cyanide fishing for aquarium fish, overuse of reef resources, and harmful land-use practices. High nutrient levels such as those found in runoff from agricultural areas can harm reefs by encouraging excess algae growth.

Live coral should be thought of as small live animals embedded in calcium carbonate. It is a mistake to think of coral as plants or rocks. Coral consists of accumulations of individual animals called polyps, arranged in diverse shapes. Polyps are usually tiny, but they can range in size from a pinhead to about a foot across. Reefs grow as polyps along with other organisms deposit calcium carbonate, (the basis of coral), as a skeletal structure beneath and around themselves, pushing the coral's "head" or polyps upwards and outwards.

Waves, grazing fish (such as parrotfish), sea urchins, sponges, and other forces and organisms act as bio-eroders, breaking down coral skeletons into fragments that settle into spaces in the reef structure or form sandy bottoms in associated reef lagoons.

Many other organisms living in the reef community contribute skeletal calcium carbonate in the same manner.

Coralline algae are important contributors to reef structure in those parts of the reef subjected to the greatest forces by waves (such as the reef front facing the open ocean). These algae deposit limestone in sheets over the reef surface, thereby strengthening it.

Reef-building or hermatypic corals are only found in the photic zone (above 50 m depth), the depth to which sufficient sunlight penetrates the water for photosynthesis to occur. Coral polyps do not photosynthesize, but have a symbiotic relationship with single-celled organisms called zooxanthellae; these cells within the tissues of the coral polyps carry out photosynthesis and produce excess organic nutrients that are then used by the coral polyps.

Because of this relationship, coral reefs grow much faster in clear water, which admits more sunlight. Indeed, the relationship is responsible for coral reefs in the sense that without their symbionts, coral growth would be too slow for the corals to form impressive reef structures. Corals get up to 90% of their nutrients from their zooxanthellae symbionts.

Types of Coral Reefs

Most reef scientists generally recognize three basic types of coral reefs:

1. Fringing Reefs

2. Barrier Reefs

3. Atolls

The differences between these three main reef types are pronounced in terms of large-scale structure. Nonetheless, there is often a good deal of similarity between them within a given biogeographic region in terms of species composition and ecological interactions.

1. Fringing Reefs

The first major coral reef type is the fringing reef, which is a reef system growing fairly close to or directly from shore with an entirely shallow (less than about 10m) lagoon, or no lagoon at all.

These are by far the most common reef type in the Red Sea and Greater Caribbean region. Fringing reefs also surround many islands of French Polynesia (South Pacific) and the Indian Ocean.

Many islands within atolls have fringing reefs often referred to as the "house reef".

Patch Reefs are outcrops of coral usually offshore but often found within the lagoon of a Barrier Reef or Atoll.

Because they are situated relatively close to island or mainland shores, fringing reefs are generally the most susceptible to coastal development, agriculture, pollution, and other human activities that result in sedimentation and freshwater runoff.

2. Barrier Reefs / Patch Reefs

Barrier reefs are reef systems that parallel the shore and are separated from it by a wide lagoon that contain at least some deep portions. Examples of large barrier reefs can be found in both the Indo-Pacific and Greater Caribbean, with the Great Barrier Reef of Australia being the prime example.

The very largest barrier reefs develop on the edges of continental shelves (e.g., Great Barrier Reef; Belize Barrier Reef). These massive reef complexes are sometimes referred to as "shelf barrier reefs" in order to differentiate them from the much smaller barrier reefs surrounding some islands found in the South Pacific (e.g, Bora-Bora).

The back reef zones and lagoons of shelf barrier reefs are often very extensive, in some cases lying over 100 miles from the mainland in some areas. In contrast, the barrier reef surrounding the narrow lagoon of Bora Bora (photo, above right) actually transitions into a fringing reef in a few places.

Patch reefs are similar to barrier reefs but they exist in small patches or shoals rather than the huge structures formed by barrier reefs.

3. Atolls

Atolls are roughly circular (or occasionally horseshoe-shaped) oceanic reef complexes surrounding a large, deep central lagoon.

Atolls are most common in the Indo-Pacific region where over 300 atolls are found, but rare in the Greater Caribbean which houses only about 10-15. The four best developed Caribbean atolls are found off southern Mexico and the coast of Belize.

Atolls can exceed 100 miles in diameter and contain lagoons several thousand square miles in extent. The best developed parts of reefs surrounding atolls are on the windward side, where wave energy is greatest.

The Maldives is actually a nation comprised of atolls. Each atoll has many islands on the outer rim and in some cases, inside the atoll.

Map showing the distribution of the world's coral reefs

Reef Divers

Sadly, like virtually every other natural habitat, coral reefs are coming under intense pressure. Many have been polluted and choked with sediment and rubbish washed from the land. Others have been damaged by coastal development, coral mining, over-fishing and collection of reef animals. Tourism too has an impact, but YOU can help to minimise the damage.

• Don't touch corals, rest on them or kick them. Corals are living animals and are damaged even by gentle handling.

• Avoid kicking up the sand. It spoils the visibility for other visitors and damages corals and other reef animals when it settles.

• Do not spearfish. This is now prohibited in most countries and spearguns are usually confiscated by Customs officials.

• Leave all corals and reef animals where they are. Corals are the 'building bricks' of the reef. In many areas shells and other reef animals have become rare because too many people are taking them. Many tourist resorts and dive operators ban collecting.

• Make sure you are properly weighted!

• Take great care in underwater caves and caverns. Avoid crowding into a cave and don't spend too long there. Bubbles collect in pockets on the roof of the cave and the delicate reef animals there can 'drown in air'.

Boat Owners

• Should never anchor on corals. They are easily broken or damaged by anchors. Tie up to a mooring buoy or jetty, or anchor carefully in sand or rubble patches.

• Mind the reef! Grounding is bad for your boat and the reef. Navigation in reef waters needs special care.

Reef Conservation

Nowadays more and more people are visiting coral reefs, to look at their amazing variety of colourful life. Unfortunately, all over the world reefs are suffering from too many visitors. Corals that take years to grow are being damaged or destroyed in an instant. Now is the time to act.

• Encourage efforts to protect reefs by visiting marine parks. Help them to be a success by carefully obeying all the regulations.

• Learn more about reef and other marine life. Your visits will be all the more enjoyable.

• Be satisfied with nature as it is. Fish feeding has a place in selected areas but is best resisted elsewhere. It disrupts natural behaviour and can upset the balance of species on reefs.

• Help keep the reef clean. Always take your own litter away, and also pick up other rubbish from the beach or reef.

• Support groups such as the Marine Conservation Society that are involved in promoting the conservation of reefs.

• Follow the visitors code. Take care of the reef not just for yourself, but for all who follow.

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