Whale sharks and manta rays are what I hope to see, but not until later in the trip, when I move down the coast to Barra, in the heart of the whale shark and manta hot-spot. At Pomene, although there is a passing chance of such megafauna swimming past, sightings are rarer and the diving focuses on reefs, fish and macro life.
Descending at Sisters, I momentarily think I am in luck on my very first dive in Mozambique. Alas, the ray that swoops past turns out to be a mere eagle ray. I am almost disappointed, until I remember that seeing an eagle ray would be the highlight of many dives.
Neville, the lodge manager, gets out his trusty water-bottle and starts crinkling it. I have heard of this trick before, but never seen it in action. Allegedly, part of the sound we cant hear is similar to that of a small fish in its death throes, so it attracts the attention of bigger fish.
Perhaps this is what catches the curiosity of a couple of grey reef sharks that dart in for a look, but it doesnt hold their attention, and we see no more of them for the dive.
Instead, we get the close-up charm of an enormous potato bass, a big grouper for those unfamiliar with the South African common name, with aspirations of growing as big as a small whale shark.
Sisters is a new site barely visited by divers and no-one is feeding the fish, so the attraction is one of genuine curiosity and then friendliness as the potato bass noses up to Neville, snuggles in for a gentle tickle, then follows us about for the rest of the dive.
The reef is a series of pinnacles of sandstone, standing up 10m from a sandy seabed at 35m and nicely modelled at instructor Steves sandcastle briefing on the beach.
Sprigs of green tree coral provide a focus for orange clouds of anthias. Bigger black and white clouds of bannerfish fill the water further above - coachmen, as they are called here.
The experience is similar for our second dive at Trojan, except that the reef is a long ledge of rock with lower visibility, being closer inshore. Instead of the eagle ray, we get a turtle.
More grey reef sharks show passing curiosity in Nevilles water-bottle, and more big potato bass take turns to shadow us as we cross their territories.
At just 18m to the seabed, I have far more no-stop time than at Sisters. Time to look around and see the horsehead-shaped outcrop of rock from which the sites name derives.
With the closest recompression facilities being in South Africa, all dives are cautious, with long safety stops.
Even so, it is my dive computer flashing in and out of decompression that curtails my time with a very
co-operative crocodilefish.
Pomene Lodge is located on a sand spit at the mouth of the Pomene river, a good four-hour drive from the airport at Inhambane and requiring a 4x4 when the road turns to a sand track and disappears below water at high tide.
The flat water of the estuary makes boarding the RIBs easy. There are no adrenalin-filled surf entries; we just walk down the sand and step aboard.
The estuary makes for a good muck dive. It has to be timed right, at high tide for the clean water coming in and slacking as the tide changes.
With that constraint I get to try it first at dusk, as we return in the dark, then a couple of days later just after sunrise.

THE SUNRISE DIVE PROVES most productive. Steve finds shrimps and seahorses on both dives, but the better sunlight of the morning dive helps him to find a frogfish, then, just afterwards, I show that I am not totally dependant on a guide by finding a sea moth.
Hermit crabs, sea hares, pipefish, octopuses, flatties and nudibranchs are almost taken for granted.
Only a few metres deep, our time is limited by slack water rather than by air or decompression. There is a 4m tidal range, and consequent currents.
Between the boat moorings is an area of artificial reef, built as an attraction for try-dives and open-water training.
Not that Steve gets to teach many beginner courses. Most divers come here because they are already in the know.
We head out across the channel with the tide to a bank, drifting in along the edge of a seagrass bed.
As the tide turns, we stay as long as we can, then head back across the current and finish by drifting along the beach until were level with the dive centre.
I could have drifted further, right back to my cabin on stilts above the sand.
The sprawling estuary is home to an extensive forest of mangroves. Off the main path of the river is a maze of small channels through which Neville navigates the smaller of the two RIBs for an afternoon excursion.
There are six kinds of mangroves he tells us, from saltwater mangroves by the sea to freshwater mangroves upriver, though I would be pushed to tell most of them apart.
The mangroves are an important nursery area for juvenile fish that live among the roots, where predators cant find them. Once big enough to survive on the reefs they make their way to sea, one reason why the area is so rich with fish life.

BACK OUT AT SEA, Playstation is a rock plateau that has been undermined to leave a network of swim-through caves beneath it. The current gently wafts through, concentrating the shoals of fish inside.
Later on my trip, at Barra, I hear that Playstation is the dive Barra instructors and guides all like to do at Pomene.
Bay Ledge and Hand are more offshore reefs, equally dense with fish and friendly potato bass. Hand has the bonus of a colony of bright blue palette surgeonfish living among the now-usual forests of green tree coral.
But it is my last Pomene dive that turns out to be the most memorable. Batfish is another shallow inshore reef, named for the big shoal of batfish that live above it. Most of the reef structure so far has been rock, but here there is significant reef-building coral, and the fish life is the densest yet.
Nevilles water-bottle trick soon attracts a resident potato bass and a trio of grey reef sharks. Unlike previous encounters, they stay around for a while, getting quite agitated as they shoulder past me in a vain search for the phantom meal thats putting out such enticing vibes.
Between sharks, I find a tiny porcelain crab tucked beneath the edge of an anemone, more lionfish and scorpionfish, then finish by getting eye to eye with another very co-operative crocodilefish. The batfish keep me company on the way up.

Tucked behind the peninsula, Barra shares the same dive sites as Tofu and thus the same whale sharks and manta rays, but the beach is considerably more sheltered, and the surf launches quite gentle. Nothing like the whitewater trial John Bantin described on one DIVER trip to the area - here he could have survived the boat launch easily and brought his Zimmer frame with him.
Bernard and Bettina, on the third week of their stay, have seen whale sharks and mantas every day. I have high expectations for our first dive at Giants Castle, a ridge of sandstone with two manta cleaning stations behind it. Indeed, a ray is just leaving as we arrive.
I follow instructions and stay on the outside of the ridge, to leave the approach path to the stations clear.
After 10 minutes staring into the haze at 29m I decide that, with no more mantas in sight, I had better photograph everything else. A pair of yellowhead snapper loiter behind the battlements of the castle. Sprigs of green tree coral grow from the top and side. Its a reasonable rocky reef with a fair display of fish life but, having just moved on from Pomene, its a bit of an anti-climax.
Finally, another manta glides in.
Too far away for a good photo, do I approach and risk scaring it away, or wait and hope it soars over me
Lack of bottom time forces my decision; I swim along the ridge and beside the manta, closing in. I get a few shots at a distance any photographer knows is too far before it peels off in a big circle, perhaps to return for another pass over the cleaning station.
We make a very leisurely ascent in the blue, good for deco safety but also an extended opportunity for encounters.
It pays off. I drift through the edge of an enormous ball of kingfish at 12m, then sight a mobula ray passing below while hanging at 3m.

RAYS ARE ON THE MENU AGAIN at Tabletops, another cleaning station.
This time its a big stingray resting on the sand thats kind enough to let me get close, but alas no mantas and no whale sharks are sighted.
On the other hand, I can now confirm that more big friendly potato bass inhabit the reefs in this area.
Barra is a bigger resort than Pomene, with cabins lined up behind the beach rather than built on stilts above it. Theyre good enough, but not in the same league as those at Pomene. For that, you would need to stay at the nearby Flamingo lodge, part of the same business and sharing a dive centre.
This centre is excellently set up for a much bigger volume of customers than are present while I am there.
Briefings use maps of the dive site and a carved wooden model RIB to illustrate the finer points of beach launch and recovery. They are extremely thorough.
Its interesting at first but gets tedious when the same divers go on receiving the same long briefing dive after dive.
Diving continues with variations on the sandstone reef theme, some nice canyons, overhangs and swim-throughs; big shoals of fish, friendly potato bass, moray eels and spiny lobsters.
Soft corals and green tree coral are predominant, nowhere more so than at Sherwood Forest. If it were not for the constant anxiety of not meeting the local megafauna, I would be appreciating the reef life more. The manta rays are not co-operating and neither are the other main attraction, despite dive centre manager Megan laying on additional whale-shark safaris at every opportunity.
My last day arrives with dives at Amazon and the Office. Plenty of fish-cleaning is going on, but no mantas
are taking advantage of the service.
Still, my day is made by the arrival of a loggerhead turtle, just as Im about to ascend from my last dive, and I stretch my time to get better acquainted.
My whale-shark hunt has become a whale-snark hunt, clutching at straws now with another safari that afternoon, and again on the morning of departure. I cant go diving, but I am out in a boat with snorkel gear running search patterns up and down the coast less than two hours before I am due to fly.
If whale sharks grew from the amount of effort put into finding them, Megan and the crew at Barra have earned a 20m giant. I am consoled with a manta ray over the sand.
Back in the UK an email awaits me. The whale sharks have returned; seven on one safari. A bloke called John from divEr has again used up the 13% quota of outings that dont see a whale shark.
Go now - youre sure to see one.

Dubbed the Manta Queen and a headline speaker at Dive 2010 this month, Andrea Marshall is based in Tofu and shares research facilities with whale-shark researcher Simon Pierce to study the resident manta rays.
Like whale sharks, mantas can be identified from their spot patterns, but this is more difficult, as the pictures must be taken from below to reveal the spots on their white undersides. More than 600 individuals have been identified off Mozambique, 80% being female and 55% of these mature.
Again by identifying individuals, overall populations can be estimated. Through this research Andrea gained the special distinction of identifying a new species. After the resident reef manta rays come the slightly larger and more migrant giant mantas.
The best clue to distinguishing them is that the giant mantas retain a vestigial sting above their tail, a relic of their evolution from sting rays. Divers often mistake the much-smaller mobula rays for mantas.
Manta rays reach sexual maturity at 6-8 and a size of 4m. Gestation lasts about a year, females giving birth to a single pup as a perfectly formed manta 1.4m across.
After this, the mother will often take a year to recover enough reserves to become pregnant again. This high-investment approach to a single offspring is opposite to the shotgun approach of whale-shark reproduction. The largest mantas are up to 8m across.

Whale-shark researcher Simon Pierce is based in Tofu in Mozambique because that is where one of the worlds greatest resident populations can be found, with the highest year-round abundance. In all, people on 87% of whale-shark trips are said to see a whale shark.
Individuals are identified through the pattern of their spots, specifically between gills and dorsal fin. Computer programs match photographs against a global database of previously identified whale sharks, with any positive matches then confirmed by eye.
Off Mozambique, 450 whale sharks have been identified, 20% of all those identified worldwide.
Four-fifths of individuals sighted in this area are young males, as is the case worldwide. So where are the females, and where are the adults Do they stay in the open ocean Do they stay deeper Or is there a huge imbalance in the population
The life-span of a whale shark is estimated as 100 years, with males and females reaching sexual maturity at 30. An adult can be 20m long, but its brain weighs only 35 grams.
After an unknown period of gestation, females give birth to a few hundred perfectly formed babies about 60cm long. This is referred to as the shotgun approach to breeding, with an estimated 90% of babies not surviving to 20 years old, as resident off Mozambique.

GETTING THERE: Fly with South African Airways via Johannesburg and onward with Mozambique Airlines to Inhambane. SAA provides an additional 20kg for dive kit, Mozambique Airlines an additional 7kg. Be prepared to have your dive bag opened in Johannesburg.
DIVING & ACCOMMODATION: John Liddiard stayed at the Pomene Lodge and Barra Resort, www.barraresorts.com. From the UK, Safari Diver provides a fully inclusive package (sample price below), www.safaridiver.co.uk
MONEY: The metical
HEALTH: Take precautions against malaria and a full set of inoculations.
WHEN TO GO: Year-round, though there is a typhoon risk in February.
PRICES: The price of John Liddiards itinerary is £1810, based on two people sharing accommodation, and includes all flights and transfers, three nights half-board at Pomene Lodge and four at Barra Lodge, and a 10-dive package.
TOURIST INFORMATION: www.mozambiquetourism.co.za