My mom will tell you I'm a diver. When I first came to Thailand, that's what I lugged over here — my dive gear. Despite being raised on Jacques Cousteau documentaries and James Bond movies, and with my marine biologist stepfather Jerry who had me exploring the tidal pools of the California coast from an early age, you may be surprised to learn that I actually didn't get started diving until I was 35 years old. Now it's the love of my life.

My folks just returned home from their first visit to Thailand. Mom was worried silly that I'd make her try diving while she was here. I have absolutely no idea why she thought I'd push her into something she wasn't comfortable doing — just because I enjoy it so much. But any case, my mother, 65 years young, just had her first scuba-diving experience in the world-famous Similan Islands, in Thailand's Andaman Sea.

For many different reasons, the Similan Islands are rated one of the 10 best dive destinations on the planet. Along with all the stunning scenery underwater, the islands themselves are postcard material, offering great hikes and lookouts atop stark grey boulders. The white sand is like talcum powder under your feet. There's always a chance of seeing whale sharks and manta rays, and other surprise guest stars. Earlier this year, two Andaman Scuba staff, Nui and Nicky, got the rare chance to dive with a transient pod of six orcas passing through on their migratory rounds. A large female swimming below opened her mouth and showed them her shiny teeth.

The nine islands of the Similan group lie about 90 kilometres off the Phuket coast. These are the desert isles that people conjure in their fantasies of getting away from it all. Together they constitute a strictly controlled Thai national marine park. You can stay overnight on two of the islands in bungalows or tents, which must be reserved well in advance through the ranger station. Or you can do as I did for this story, and book a trip with one of the many live-aboard dive boats that travel out to the islands.

We left from Patong Bay in the evening for a four-day trip. The Thai staff aboard Bummee 1 had been busy on the boat all day. Tanks topped off, galley stocked, coolers full of ice, rooms clean, beds turned down. The other divers are often some of the more interesting creatures you encounter when diving. Andaman Scuba is a French-owned company, so we had quite a few French divers, some from Belgium, a few Israelis, and me — the solo American. I assembled my dive gear for the morning as a giant string of firecrackers banged off the bow, lighting the night with 1,000 flashes, and marking the beginning of our journey with the blessings of the sea gods.

The nice thing about leaving at night is that it's a long boat ride, and I spent it dreaming in the octopus's garden. "Wake up. Wake up, Mr Reid." My old friend Nui the dive-master chortled. I looked out my polarized cabin window to see the giant blazing star that lights our world rising from the sea. Still partially clothed in a nightgown of wispy clouds, the sun presented a spectacular vision, and so did the Similan islands.

Cartoons at Barracuda Point: Our first dive site was Barracuda Point. Often dubbed "the rainforest of the sea", these coral reefs present more wildlife in the first 10 minutes than you see in a year on land. We spotted a common reef octopus right away, and I watched her watching me with her suspicious, surprisingly intelligent eyes. Suddenly, she shifted colour, becoming indistinguishable from the coral and rocks she poked from. A small fish suddenly became the object of the octopuses ire, apparently for revealing her hiding place. A lightning-fast tentacle meted out a quick backhand volley. The traitor fish quickly got the message and scooted off.

The morning dive was long and slow, with Nui's shaker — a device to alert customers to something she wanted to show them — nearly in a constant rattle. There was just so much to see. Tiny cleaner shrimp running their ever-popular service station for all the fish who need to look sharp; big moray eels poking from crevices, gills pumping and mouths agape; vivid nudibranchs out for a sea-slug stroll; the comical and shy little boxfish scooting under the staghorn coral with its underpowered fins working over- time. And the schools of fish swirling in and around the coral heads, each species attuned to the movements of its own kind, put on endless light-and-dance shows in the underwater ballet we swam though. You could actually forget to breathe down here.

Aerials over Deep Six: We moved on to Deep Six, a boulder dive featuring the same underwater topography that made up the islands themselves. Here you experienced that sense of flying that people use to describe scuba's weightless world of anti-gravity. It was as though you were a helicopter roving the peaks of a mountain range. A different crowd of sea life hung out in the big rocks. Skipjacks, barracuda, and large tuna school patrolled their turf around the outer edges, darting in every so often to incite frenzy in the swarming schools of other species. A number of swim-throughs, where boulders rubbed shoulders, presented intriguing prospects. When you popped out into the light on the other side, there was always a huge crowd of larger fish waiting to see who was coming for dinner.

Golden Eyes of Anatto Bay: Next we explored Morning Edge, another beautiful coral garden featuring giant sea fans, towering hard coral heads decorated with soft corals waving in the tide, and the dazzling array of creatures that call them home. In the evening, it was Anatto Bay for a night dive. We spotted a couple of painted lobsters and many of the large red crustaceans known as "splendid crabs". Millions of golden eyes peered out from everywhere, tiny crustaceans working the night shift.

Shark encounters at Breakfast Bend: It was day two, and we were visiting four sites — the Arches of North Point, Breakfast Bend, and a couple more around Koh Bon in search of manta rays. The Arches, mainly a boulder dive, ended in a spectacular coral garden. But Breakfast Bend, a long underwater ridge, turned out to be a shark dive featuring up-close encounters with five leopard sharks we found resting at the bottom. These are completely harmless sharks, with grinding plates instead of the rows of teeth displayed by most of their cousins. They allowed us to swim up and rest with them, sometimes swimming off and gliding around us, propelling themselves with sweeps of their huge tails.

Live theatre at Koh Bon: This island is not actually one of the Similan Islands, but lies within easy range. An amazing seamount presents an underwater amphitheatre, a common place to swim with giant manta rays. The whale shark, the world's largest living fish, also appears here. But this day the theatre was empty. Nevertheless, we were treated to another shark encounter, this time with the shy, slender white-tip reef shark. Even in the absence of the giant marine life, this dive site is just outrageous. We worked against a strong current for the beginning and then let it carry us around the bend for the second half of the dive. A beautiful sea turtle had the same idea riding along with ease and grace.

In the afternoon, I offered to take Ariela, a first-timer, on a shallow reef dive. One of the three from Israel, she wasn't planning to dive, but she soon conquered her fears, and wound up having a blast, eyes wide the entire time. Some of the other guests went night diving, but I'd had my four dives for the day, and stuck around for a game of cards and a beer or two topside. My new friend Phillip bought me too many beers and, together with the Thai captain, we disturbed the peace with a few rousing tunes.

Chang-over at South Point: Upon waking next morning near Koh Tachai, I felt as though I'd been hit by a truck. In fact, I had a Chang-over. Like any other, this job has its occupational hazards, and Chang Beer is merely one of them. Once in the water, I got quickly sorted, and winged along with the group. Since when had it become routine to see so many sea creatures in such great visibility? We could see forever through a silver curtain of darting marine life.