THE BRIEFING SHOULD HAVE STARTED BY NOW but chaos has overtaken us. The dive deck is deserted as the excited guests spread out, busy photographing the extraordinary landscape of the island.
They admire the clumsy boobies which fly over us in search of the best landing place, decorating the decks with their large droppings as they do so.
I look one bird in the face and note what must be one of the most ridiculous expressions in the animal kingdom.
Pat and Gary Bridgford from Kansas, who have come on this trip to celebrate their 30th wedding anniversary, approach another young bird. Gary places his hand under its feet and, confused, the bird hops on.
Over the years, as my fascination with and understanding of the marine realm has grown, I have become an earnest believer that we do not have the right to touch anything under water except dead coral or bare rock, and then only if it is really necessary.
So when we finally settle down to our briefing, and our dive guide Jose Luis tells us that the manta rays here enjoy being touched, my doubts arise.
He says gloves are forbidden because they often hold bacteria that can be transmitted to the mantas skin and ultimately kill it. There are three sensitive places that we should avoid - the tip of the wings, tail and around its eyes and mouth. Otherwise we can touch them as much as we wish. The fact that the same mantas have been here for years and are all well and happy surely indicates that this is true!
A giant stride off the Solmar Vs back deck places us next to a heavenly pinnacle that starts at 8m and drops to a sandy bottom at 36m. Its a manta rays cleaning station called the Boiler.
We start our descent at once and dont know what to be more excited about, the haunting sound of a singing whale or the giant manta that is heading towards us with great speed and determination.
Pat is the first to raise her hands. The response is immediate. The manta makes a sharp turn and places itself above Pats head. She touches it with her hand and thats it - the two immediately take off in a graceful dance.
For a while I watch this enviously. The manta does not seem interested in anybody else. Yahoo - Im here! I raise my hands, hoping its not the loyal type, when Gary points behind me. Another, even larger, manta is heading my way.
She slows down and clearly wants me to join her. On her belly is a beautiful pattern of black and white markings. Wow, nature really did well on this one!
Every manta has different markings, similar to the pattern on a whales tail, or a human fingerprint.
I turn myself to face this pattern, and with the gravity of her size pulling me closer we glide confidently into a gentle ballet. With the sound of a singing humpback vibrating through every tissue of our bodies, this moment is ecstasy. When I cant take it any longer, I place the palm of my hands against her skin, which feels like the rough side of a Velcro patch. She quivers.
I remove my hands for two seconds, then touch her again. She quivers once more and becomes motionless. We start sinking slowly.
I would have kept going, but with all the excitement I neglect the simple task of clearing my ears. I slide away from under her and move towards the shallow rock to join the other divers.
She follows as a third manta arrives, then a forth and then a fifth.
Manta rays live in tropical waters and feed on plankton, using their frontal flaps. Their wingspan can reach 7m, their weight 1300kg and they can live for 60 years or more.
The Boiler is the only known manta cleaning station in the world where the rays have adapted to such friendly behaviour. Over the years they have learned to believe that part of the cleaning process includes bubbles and a human hand.
Many of the mantas we see here have two or more large remoras fixed to their flesh. The remoras themselves are covered with little parasites, crustaceans called copepods. Together with bits of mantas dead skin, these provide a tasty meal for the cleaners, the endemic clarion angelfish and blue-spotted jacks.
We soon run out of film. We have almost finished the short swim back to the boat when I look back. My feeling was right, we are not alone.
The Solmar V is a 112ft luxury yacht with a Mexican crew of seven plus three instructors. Well-equipped with side-scanning sonar, radar, long-range communications gear and two compressors, it can carry 22 passengers and offers four or more dives a day.
We cruise during the early hours of the morning and wake up at Roca Partida, the smallest of the four volcanic Socorro islands. It measures only 45 by 90m, and in fact is not an island but a large rock rising high above water level and smothered with white bird droppings.
Being lost in the middle of the ocean and mounting from great depths is what makes this rock such a unique dive site for those in search of the big stuff.
The Socorro (aka Revillagigedo) islands start 220 miles south of the tip of Mexicos Baja California peninsula. San Benedicto is the closest, Socorro is 22 miles further south and to the west are Roca Partida and Clarion, which is 370 miles off Bajas tip. Owned by Mexico, the islands are uninhabited except for a naval base on Socorro.
We drop straight down to 40m and find ourselves in a thick gathering of fearless sharks. Galapagos, silvertip, whitetip and silky sharks are everywhere. They are not aggressive and keep a respectful distance from us.
We start swimming along the sheer rock, nearing a big school of jacks. They notice us and reposition themselves as a black cloud hovering in the blue. When the initial thrill is over we turn to the wall - which is pink.
We realise that it is covered with Panamic green morays. Not only do they swim freely from one crevice to another, but they are also happy to share their homes. Four or five morays dangling out of one hole is a common sight here - Moray Hotel, as Pat later calls it.
As we near the rocks tip, a school of 20 dolphins suddenly appears. They come close for a curious look and then disappear as fast as they came.
There are fewer sharks now. We arrive at the tip, starting a slow ascent when around the corner we see the first scalloped hammerheads, about 10 of them. We look up to see at least 30 more of these amazing creatures silhouetted in the clear water. This is what divers dream of, and here it is. The surface can wait.
We try to swim closer, but the hammerheads turn away in perfect formation. After an exciting safety stop, during which a solitary hammerhead comes for a too-close-for-comfort look, we board the panga and start heading back to the liveaboard. Thats when the school of dolphins reappears.
With our masks and fins we leap in quickly and are delighted when they give us a playful welcome. Gary is the last to jump in and hits something in the process. He looks down quickly and thinks: Hey, thats not a dolphin - its a shark! In moments at least 12 silky sharks are circling us. Jose Luis feels that it might be wisest to leave.
Dramatic red mountains, covered with little green patches and steep layered cliffs provide a perfect background for the numerous breaching whales, and a pod of about 15 humpback whales which cruise past us as we arrive at Socorro.
The island is the largest of its group, about 100 square miles, and a popular refuge for hundreds of humpbacks escaping the Arctics cold winters. They come here to rest, mate and give birth.
Just before the dive Jose Luis tells us that we can expect company. How he knows that is a mystery.
We start at 30m on what used to be a cave, but at some point its ceiling has collapsed, creating a large, photogenic arch. Arent we lucky Visibility is at least 40m, and once again we can hear, loud and clear, a singing whale.
After a brief photo session we move on to some bare but dramatic rock formations. Our attention is drawn to two whitetips and, before we know it, Jose Luis is leading us into another large opening in the rock. If you like lobster, this is Lobster Palace.
The Socorro spiny lobster, unlike others, has bright blue markings at the base of its antennae. With hundreds of these enormous crustaceans lurking around, like giant cockroaches, this is the perfect scene for a horror movie.
Back in open water, we are delighted when a curious manta ray makes her way towards us. Is this what Jose Luis meant For a while we take turns to try to approach her and find that, although untouchable, she chooses to stay near us.
We hear the clicking and squeaking only seconds before they show up. Gary is the one who points them out to us, and he does so in such a calm manner that one would think he see pods of 16 bottle-nose dolphins every day.
Four of them, as if reading each others mischievous thoughts, branch away and make their way to us fast and in formation. They playfully aim for Gary and, just before impact, shoot upwards. Now he is excited.
During our remaining 20 minutes the dolphins keep disappearing and coming back, as if asking us to join them. When its time to go back, they follow us to the panga and then escort it as we make our way back to the liveaboard.
As we lie on the sun-deck, the Solmar V starts the cruise back to San Benedicto, our last stop before the return trip to Cabo San Lucas. The sun is shining, the sea is calm, the whales are breaching and a large pod of dolphins comes to escort our departure.
In only three hours we will be in the water, caressing those amazing mantas again. This is one wedding anniversary Pat and Gary will never forget.

Yes, we know that we always say don't touch anything under water, but it seems that these unusual Socorro manta rays, seen here at the Boiler site with Tally Pozzoli, like to dance close up
The dolphins arrive at Roca Partida, smallest of the Socorro islands
bottlenose dolphins at play
boobies strike a Titanic pose on the boat
the scalloped hammerhead sharks were already there - silky sharks were just arriving
the panga set against a dramatic lava-rock backdrop at San Benedicto
the Solmar V liveaboard makes the long trip out to Socorro
a breaching humpback whale
One of the big Socorro spiny lobsters
eel in residence at the Moray Hotel
an octopus


GETTING THEREAmerican Airlines and Continental fly from London Heathrow to San Jose Del Cabo in Mexico, via Chicago, Dallas or New York/Houston. Fares start at around£560.
DIVING & ACCOMMODATION:The Solmar V is based in Cabo San Lucas and takes divers to the Socorro Islands and the Sea of Cortez. It is air-conditioned and has 12 staterooms with private bathrooms, TV and VCR.
COST: An eight-day trip to the Socorro Islands on Solmar V costs around£2000.
WHEN TO GO: Almost every hurricane created in the Pacific and headed for Central America visits the Socorro Islands between June and October. Most stable conditions are from November to early December, April and May. Water temperature is around 27C in autumn and 21C in spring.
FURTHER INFORMATION: Cabo Resort Reservations, 001 800 344 3349, www.solmar.com