Reaching new depths

I was used to watching enviously from the shoreline. Boats packed with divers would make for wrecks set down in 30m (100ft) of water and I'd be a spectator. "Only advanced divers on this trip," would be the announcement from the dive centre. Later, when the boats returned, I'd listen in awe to the tales of sunken vessels and enormous fish.

I was used to watching enviously from the shoreline. Boats packed with divers would make for wrecks set down in 30m (100ft) of water and I'd be a spectator. "Only advanced divers on this trip," would be the announcement from the dive centre. Later, when the boats returned, I'd listen in awe to the tales of sunken vessels and enormous fish.

Any basic scuba qualification (in my case a PADI Open Water) allows the diver to descend no deeper than 18m (59ft). It's a reasonable limit that gives ample scope for a safe introduction. But if you want to see the really cool stuff you have to be trained and certified to go deeper.

The internationally recognised PADI Advanced Open Water course prepares the diver to reach depths of 30m plus. It grooms existing scuba skills and introduces you to a whole series of speciality underwater techniques.

Which is why I find myself sitting on the deck of a converted fishing boat, enjoying the bright tropical sunshine. A string of islands - part of an archipelago just off Thailand's eastern seaboard near Pattaya - cut into the horizon, green woodlands contrasting with the deep blue skies and shimmering turquoise seas. The boat is filled with neatly stacked racks of cylindrical dive-tanks. Several wetsuit-clad figures are moving around, checking equipment, connecting the dive-tanks to their BCDs (buoyancy control devices) and loading the rigs onto their backs. I finish sunning myself and begin to do the same.

"This will be the first dive of your PADI Advanced course," says my instructor, Vinny, a 48-year-old German who works for Seafari, a Pattaya-based dive centre. "We'll be descending to a depth of 30m, to the edge of the Khram, an artificial wreck, where I'll be taking you through some simple tests."

The best thing about the Advanced course is that you do most of your learning in the water. There are two requisite dives (a navigation dive and a deep dive to 30m) and three elective dives (chosen from a range of 35 electives that includes everything from wreck diving to underwater photography).

Unfortunately, for those who don't like studying, the course doesn't begin in the water. In true PADI fashion it begins with an explanatory video and a textbook. In order to make my deep and navigation dives - the first day's focus - I must complete two knowledge reviews.

The book is an illuminating read. Diving to 30m-plus is a whole new ball game. Air consumption, caused by the extra compression that occurs at this depth, is extremely rapid and can cause breathing problems. Buoyancy, essential to maintaining control when diving, can also be difficult. The extra compression also has another major effect - nitrogen narcosis. As the air breathed gets thicker with the pressure, the concentration of nitrogen increases. The resultant narcosis can turn the diver into a pubescent teenager: inappropriate behaviour, undue anxiety, euphoria, and short attention span. In any other situation this would be amusing. In 30m of water it can be deadly.

Theory never matches practice but as we begin the dive at least I know what to expect. We follow a fixed line down to the Khram - an ex-US landing craft, re-commissioned by the Thai Navy and then sold and sunk to provide a dive attraction. There are four divers in total - Vinny, myself, Troy (an Australian also taking the Advanced course, and my appointed dive buddy) and Scot (an experienced American diver).

The Khram looms into view, its superstructure fused with thousands of barnacles, and swarms of tropical fish darting around the rusting hull. There's sand at the bottom and we come to a gentle stop, resting on our knees. I notice that with each breath I am sucking in vast quantities of air - my lungs labouring as they force it through my regulator.

Vinny points at me and hands me a slate with a series of maths questions. Initially, I am confused. Maths questions? It slowly dawns on me that he wants me to answer these questions. He told me about this before the dive. I go through them as fast as I can. Vinny times me. I take 35 seconds. He then shows me some pieces of coloured cloth. They are dull shades of green, grey and blue.

After Troy has completed his tests we carry on with the dive and move along the length of the Khram. A shoal of barracudas swims beside us, luminescent eyes staring quizzically. We enter the trough of the landing craft and more barracudas arrive. Driven by curiosity and with mouths gulping they approach to touching distance.

At this depth the PADI manual recommends that "buddies" (a simple safety system of pairing divers together) check each other's air and depth gauges. We entered the water with 220bar of air and need to make a five-minute safety stop at 5m. A basic safe rule of thumb is that no diver should leave the water with less than 50bar. Troy has 120bar; I'm down to 90.

I get Vinny's attention and hold up nine fingers. He nods, waits for the other divers to come in close and gives the thumbs up - the universal diver's signal for ascent. We complete the safety stop and I climb back into the boat with 60bar. No problem.

The dive leaves me exhilarated and excited. I want more, but for today at least, another deep dive is off the cards. The rich, concentrated air breathed at depth fills the cells of my body with nitrogen and oxygen. These gases, which are toxic at high levels, need time to vent off.

Vinny hands me a piece of paper with the same maths questions I'd completed at depth. "I'll time you again," he says. I take 15 seconds. He also hands me the coloured cloth - now a rich play of bright reds, pinks and purples. "The lack of light at depth has a dramatic effect," says Vinny.

We lunch on the boat and Vinny briefs the group on our next dive. "This will be a shallow dive, no more than 12m," he says. "Andrew, you will be completing your navigation dive. I want you to take us to the reef about 100m off the bow of the boat, navigate a square and then return to the anchor line."

Navigating underwater is the same as on dry land: you use a compass. However, on dry land you can see physical features in the far distance: buildings, hills and trees. In the sea, visibility is dramatically curtailed. Here, it's down to 12m.

My previous night's reading of the PADI manual introduced me to certain physical features that exist under the sea. For example, ripples in the sand are always perpendicular to the shore. It also suggests speaking to divers who know a particular dive site well. Each site will have specific features - large rocks, corals, currents, reefs - that can guide the diver.

I set my compass on the boat, get in the water, and head in the direction of the reef. Vinny gives me a few minor directional adjustments but we arrive on our target. We take in the superb, psychedelic coral bed. Suddenly, Vinny darts for a rock, shoving his hand underneath. He has found a puffer fish. It sails out fully inflated, covered in nasty looking spikes, its tiny fins rotating in fury.

We leave the puffer behind, I complete my "square" - it's actually more like a collapsing oblong - and then, with Vinny's helping hand, guide us directly back to the anchor line.

After an hour on deck, it's back in the water to complete the first of my three elective dives - Peak Performance Buoyancy. The other two - Wreck Dive and Boat Dive - will be completed tomorrow.

"Good buoyancy is essential to make a controlled dive," says Vinny. "You'll need to do this to penetrate a wreck effectively and safely. Making sure you are correctly weighted for the conditions is very important." I've been diving with 5kg of extra weight but Vinny tells me to reduce it to 4kg. "You want to be neutrally buoyant throughout the dive," he says. Once in the water I empty my BCD (this keeps me afloat) and hover just below the surface. With each inhalation I rise and each exhalation I fall. A couple of gentle kicks ease me downward. I control both my breathing and my buoyancy effortlessly.

The morning arrives with an hour's drive to the village of Samesan where we meet a local fisherman and his cute, brightly painted boat. "He's been working with us for years," says Vinny. The Boat Dive is straightforward enough - basic boating skills coupled with dive boat etiquette (don't leave all your heavy equipment in a mess on the deck) and different entry techniques (roll backward commando style off a small boat and jump in from a larger one).

The final dive of my Advanced Course is the Wreck Dive. A Thai freighter, the Hardeep, sunk by a French fighter pilot in 1941, lies in 30m of water. We'll be making a wreck penetration - entering the stricken vessel. With jagged metal, mounds of silt waiting to be kicked up into thick clouds and small spaces within which to move, all in 30m of water, this will challenge all my dive skills.

We move along the length of the wreck to an opening. I follow Vinny in, scraping my tanks along the ragged edge of the hole. I adjust my position, but over-compensate, hit the floor with my fins and kick up a plume of silt.

Vinny moves on through a short, spacious passage. This time I make it through without incident into open water. I quickly check my gauge - I have about seven minutes of air left at this depth and need to move to shallower waters to conserve air.

Suddenly, a shape looms out of the water. Vinny raps his tank to get my attention and points. It is an elegant, enormous sea turtle - one of the most awesome sights a diver can witness. We follow its gentle upward arc for a couple of minutes, lost in the sweeping motion of this spectacular creature before making for our final safety stop. My Advanced course is complete. The combination of the turtle and the Hardeep has left me speechless. "The best always waits until last," says Vinny, as we make for the shore.

AFTER THE TSUNAMI: DIVING IN SOUTH-EAST ASIA

The effects of the Asian Tsunami on the waters around South-east Asia have yet to be quantified. While the Andaman Sea was hit hard, the waters in the Gulf of Thailand and the majority of Indonesia were totally unaffected; dive destinations such as Thailand's Pattaya and Koh Tao are in excellent condition.

Many of the national marine parks of the Andaman Sea, including the dive sites around the Koh Similan islands (off Phuket), have re-opened.

Scientists are still assessing the situation but some predict that marine life could take generations to recover. What is already certain is that many coral beds have been wiped out. There are also many reports that underwater visibility is the clearest it has been for 10 years, the tsunami having cleared everything out. Many local dive companies on Thailand's western Andaman coast are suggesting that dive sites have returned to normal. Travellers would be advised to wait until the situation is fully and independently evaluated in the Andaman Sea before booking expensive dive holidays.

In the meantime try the following:

The purpose-built luxury dive yacht Panunee offers live-aboard dive trips and charters to the best dive sites in South East Asia from US$420 (£230) including all dives and food while on board (does not include flights, transfers etc). www.panunee.com

Seafari, based in Pattaya, is South-east Asia's oldest dive school and a five-star PADI Dive Centre. Instructors and staff are some of the most experienced in Thailand. A two-day PADI Advanced Open Water course, including equipment, lunch, soft drinks and boat fees costs 12,000 baht (£170). They can also arrange leisure dive trips to the Hardeep and Khram wrecks, local islands and dive sites. 00 66 38 429 060; www.seafari.co.th

The island of Koh Tao, in the Gulf of Thailand, is home to the largest number of PADI instructors in South-east Asia and is one of the cheapest places to learn to dive. One of the best places on the island is Coral Grand Resort which provides both dive school and stylish accommodation. 00 66 2 629 2916; www.kohtaocoral.com

DIVE DOCTOR: CAN I DIVE WITH...

...ASTHMA?

Asthma is a lung disease that causes the airways to tighten up during an asthma attack. When you are breathing air at depth whilst diving, that air assumes the pressure of the surrounding water, so air pressure is higher the deeper you go. If this air were to become trapped in the airways during an asthma attack, it will expand as the diver ascends to the surface and cause lung damage.

In some countries there is a blanket ban on any asthmatic diving. However in the UK we are a bit more realistic. The diagnosis of this condition falls into a broad church. It ranges from the person who wheezes after only a light jog, to someone who once suffered in childhood, but still carries the diagnosis into a trouble-free adulthood. The rules in this country are that a well-controlled asthmatic has as much risk of lung problems underwater as a smoker, and they are allowed to dive. With such a wide range of asthma sufferers, you see how it is possible for many of them to dive. If your dive doctor feels your lungs are fine after testing them with a lung function test, called spirometry, then you may be fine to dive after all.

...HIGH BLOOD PRESSURE?

Blood pressure is a figure made up of two readings. It is expressed as the systolic pressure (the amount of work the heart has to do to pump the blood around the body) over the diastolic pressure (an indication of the pressure needed to refill the heart). A normal reading is about 140/80.

The higher your blood pressure (BP), the more risk there is of heart attack and stroke. This would be potentially fatal underwater, so there are rules that govern diving and blood pressure. If a BP exceeds 160/100 then you are barred from diving. But a lot of readings can be artificially high when you rush in to see the doctor - even the process of seeing your GP is enough to raise it, so called "white coat hypertension". So make sure several readings are taken. If it is high and you are desperate to dive, then weight loss, exercise and medication can reduce the pressure and allow you to dive after all. Some medications are better than others though, so stay away from beta blockers, eg. atenolol, as they can affect the lungs whilst diving. Try one of the newer tablets like losartan as they are safer.

...AN EAR INFECTION?

When you descend on a dive, the surrounding water exerts pressure on the body. Solids and liquids are fine: they stay the same. Air spaces, though, will contract and need the pressure in them to be increased to be the same as the depth you are at. This is called equalization. The main spaces that need to be equalized are the sinuses and the middle ear. A simple Valsalva movement, like stopping a sneeze half way through, will do this. The problem with a middle-ear infection is that the inflammation will stop air from entering this area, so equalizing becomes impossible. If you dived with this, the remaining air would contract and damage the ear drum and windows into the inner ear where the balance centres are. This would result in a permanent ringing and even deafness.

So if you suspect you have an ear infection, see a doctor, start antibiotics if needed, but don't dive until it is fully better.

Dr Jules Eden is a Diving Doctor at the London Diving Chamber in St Johns Wood, London (020-7806 4000; www.londondivingchamber.co.uk)