As I woke to the sounds of gunfire, thoughts of far eastern piracy flashed through my sleepy brain. Fortunately, before diving for cover under my bunk, I recalled the Thai custom of letting off fire-crackers on the bow of a boat as an offering to Buddha before sailing. I relaxed with the pleasant realisation that we were departing for the Andaman Sea to some of the best diving that Thailand offers. 
I  was aboard the Seraph, a beautifully restored schooner which was rescued from the reefs of the Andaman where she ran aground in 1991. Mark Harwood of South East Asia Divers bought her as an insurance write-off then re-caulked and repaired the hull before towing her to Phuket. Here she was restored to her original sail design of a gaff-rigged schooner and had luxuries such as air-conditioning fitted.
Now she is dedicated to adventurous diving and was creaking gently as we headed towards our first destination, the Similan Islands some 60 miles away.
This collection of nine islands was declared a Marine National Park in 1982 as protection from the ravages of over-fishing and dynamiting. On the eastern shores, which are sheltered from the summer monsoon winds, there are reefs constructed entirely from coral. However, most of them are made up of hard and soft corals adhering to massive boulders or outcrops of granite.
Bird Rock, off Similan Island 7, is typical of the area, with many huge boulders on the seabed forming tunnels, swim-throughs, deep gullies and caves. I found areas of lush, healthy hard and soft corals and sea fans, especially in the gullies and tunnels. Some of the rocks had almost sheer walls falling to 30m where there were some very large barrel sponges. There were plenty of reef-fish in evidence with shoals of fusiliers, unicorn surgeons and groups of harlequin sweetlips.
I spent most of my dive around the barrel sponges searching in vain for frogfish, only to find the rest of the group gathered around a striking orange example in just 10m of water, posing nicely on a plate coral. His colour did not blend perfectly with his background, but he was nevertheless convinced enough of his camouflage to allow me to make a very close approach for photographs.
About half a mile west of Similan Island 2 is an open-water site called Boulders which, unsurprisingly, comprises a series of massive granite boulders on a rocky/sandy seabed. Swimming down we spotted a leopard shark resting on the sand at 27m.

The walls of the huge boulders were covered with dozens of huge gorgonias and trees of deep green tubastrea corals. Reaching one of the plateaux at 15m I was attracted by the attacking movements of a shoal of jacks targeting a dense shoal of glassfish by a large table coral. Under the glassfish was a group of about 18 lionfish ranging from juvenile to adults resting or languidly hunting. As I focused in, I realised that there were at least half a dozen bearded scorpionfish among the coral rubble. This made getting a low angle on the scene a little more interesting!
Elsewhere most species of reef-fish were darting about in ones and twos and occasional shoals of Spanish mackerel and chevron barracuda swam past. There were some soft corals here but otherwise the site was dominated by table, plate, mushroom and brain corals. The current can often be quite strong, so dont forget your safety sausage!
The Surin islands lie 60km north of the Similans, just a few kilometres from the border with Burma. This area is again a Marine National Park and consists of five granite islands and two rocky islets. The larger islands are covered in lush primary rain forest and also have extensive areas of mangroves in their sheltered bays. The shallow-water coral reefs are in better condition here than in the Similans, particularly at Koh Torinla, which has a magnificent staghorn reef.
A series of submerged pinnacles and plateaux close to Surin is known as Koh Tachai. We found one pinnacle which was set apart from the more dived area marked out by mooring buoys. Here we descended to a seabed at 21m strewn with large boulders with very impressive sea-fans and soft corals all feeding in the stiff current. Sheer walls loomed around the large granite pinnacle, also festooned with fans, soft corals and plate corals.
This pinnacle is obviously less dived than others as the top of the rock is in excellent condition and is covered in large brain and mushroom corals, with masses of purple soft corals and several different types of large gorgonia. There were hundreds of reef-fish here: large dusky sweetlips, blue-lined snappers, silversides, chromis, Spanish mackerel, the odd marauding jack and shoals of garfish. Macro life was also particularly rich, with great swathes of tubeworms on the hard corals and all sorts of symbiotic life in the anemones and sea fans.
A few miles south of Koh Tachai is Koh Bon, another large limestone rocky island. The location is known for repeated encounters with manta rays, so my dive here was filled with high hopes. Visibility was good at 25-30m as we dropped on top of the submerged ridge. Almost immediately a shadow passed over us as an enormous manta cruised above. It circled only once, but for the next 40 minutes I hung close to the ridge watching out for the clouds of plankton which often bring hungry manta rays. Below me large shoals of silversides and glassfish were being hunted by jacks and snappers in the early morning light.

Eventually a dense cloud of plankton approached the ridge and I could detect flashes of white on its perimeter. The shape of the manta slowly emerged but I was horrified to see another diver with a camera swimming fast towards the animal. This proved not to be the right approach and the manta banked away almost immediately. I decided to move into the cloud of plankton in the hope that it would return, only to discover that much of it was of the stinging variety - Thai mantas obviously enjoy their spicy food!
The manta finally reappeared on the edge of the cloud, making repeated passes to scoop up the plankton soup. I focused rapidly and hoped the exposure was correct. Its attendant remora hopped constantly from the top to the underside of the animal as it changed attitude to gulp another mouthful. I realised eventually that I was drifting deeper with this graceful giant and air and time were running low. I had my last look as the manta continued to spiral around the plankton below me. It was a magical dive.
East of the Surin Islands, close to the Burmese border, is Richelieu Rock, renowned for its whale shark encounters. Chatting with several dive guides in Patong before I left gave me the impression that if the whale sharks and mantas didnt show then Richelieu Rock had nothing else to offer. The reality wasnt quite as stark as that and, while we saw nothing big during our dives, the site was interesting, particularly for photographers.
We arrived to find remarkably good visibility and virtually no current. Unfortunately those are the wrong conditions for whale sharks, which like plankton and strong currents, and we didnt see any.
The macro life here is excellent. You do of course have to close your mind to the prospect of missing something big swimming by while you are concentrating on the reef ahead, but my experience was that the other divers in the group would make enough noise if something worthwhile turned up!
Some of the best coral reefs in the area were at Koh Torinla. The reefs are shallow (2-20m) and comprise mostly hard staghorns, brain, plate and mushroom corals gently sloping from the surface and ending at a flat sandy bottom where rays and leopard sharks are often seen. There is profuse reef-fish life including shoals of fusiliers, batfish, chromis, sergeant- majors, fusiliers, juvenile barracuda, snappers, glassy sweepers and baitfish. The impression is of constant movement and activity. Even in the shallows we saw several small blacktip sharks, wahoo and large turtles ambling by.
We also dived at night here, under our mooring. The skipper secured some discarded fish heads to enable us to get closer to the sharks! This method was extremely effective, although Im not sure who got the bigger shock when the sharks and a couple of large morays made a boisterous appearance.
The reef night-life, particularly at the macro end of the scale, was absorbing and the entire reef had a surreal feel to it as we explored under a bright, rising moon.
The diving at these locations offers endless variety and an itinerary could be tailored to suit the interests of a particular group. The extreme northern and southern sites have become well-known for the reliable sightings of whale sharks and there are now several operators offering whale shark safaris between March and May. There are of course no guarantees in this world. In two weeks I didnt see a single whale shark but of course those on many other boats did! Luck has to be on your side, but we did see many large pelagics and the encounters with manta rays were extremely memorable.
  • Mark Webster was a guest on the sy Seraph, which is run by South East Asia Divers (00 66 76 344022). Trips can be arranged through Oonasdivers (01323 648924) and cost around£1260 for a seven-day trip.

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