SURROUNDED BY THE BLACKNESS OF THE NIGHT, OUR SHADOWS DANCE ALONG THE UNEVEN SEABED. The powerful lamp under the boat attracts a thick soup of plankton - the bait for our quarry. As we hang motionless in mid-water, our torches scan the darkness like searchlights in a night sky.

Its not long before one of the beams reflects a flash of white from the underside of a manta rays pectoral fin. The beams close in and focus on the manta, as it moves closer and begins to circle us.

Three others soon join the lone ray. Together they move through the water like birds of prey gliding in the wind. Their giant, wing-like fins propel them at speeds that make it difficult for us to keep track of them.

After a few minutes of this underwater ballet, one manta breaks off and dives towards the seabed. Just before it reaches the bottom, it exposes its white underside and strikes up towards the surface. It stops its ascent at the lamp and the plankton cloud. As it starts to perform somersaults, its cephalic fins at the side of its mouth stretch out to form a funnel to scoop up the nourishment.

The others soon join the lone diner. We watch in awe as they enjoy their after-dark buffet.

The site is Manta Ray Village, off the Kona Surf Resort on the Big Island of Hawaii. For several years, the powerful lights that shine from this hotel have been a magnet for plankton, which in turn attracts the manta rays from nearby deep water.

This phenomenon is by no means guaranteed. We had been waiting for more than three hours for the performers to appear, by which time the smaller dive boats had left and we were starting to resign ourselves to a long wait.
This wasnt a problem for us, however, because we were on the luxury liveaboard Kona Aggressor II, where waiting meant curling up in a warm bunk or just watching the night sky from the sun deck.

Manta Ray Village is probably one of the more unusual diving experiences in the world, ranking alongside Stingray City in the Cayman Islands and the schooling hammerheads of Cocos. Its the kind of diving for which the Kona coastline isnt famous yet, but soon will be.

The crew saves the manta experience until the end of the week, a sensible choice as there isnt another dive along this coastline to match it. The week starts in the small town of Kona on the islands west coast, where the sleek shape of the Aggressor dominates the harbour.

Our captain wasted no time in heading south, away from the inhabited areas of this already sparsely populated island. Apart from a few beach-houses, this was the last time we would see any signs of life along this still-volcanic coastline for five days.

Our first stop was a check-out dive at a site called Amphitheatre. The terrain was typical of many of the shallow sites we were to visit, a small wall surrounded by ledges, spurs, grooves and all of it in good visibility. There were plenty of fish: blue-striped grunts, moray eels, butterflyfish, bright yellow trumpetfish and multi-coloured wrasse. But the marine life wasnt what attracted me - I was keen to dive the highlight of this site, a 40m-long lava tube that winds its way from the land into the ocean.

The entrance is deceptive, as it looks like the opening to a small cave, just wide enough for one diver. Its only after a few fin-kicks that you realise youre inside a long tube caused by volcanic activity.

As molten lava flowed into the ocean, water cooled the outer layer until it solidified. However, the water couldnt stop the lava from flowing inside, and as the river of red-hot rock flowed into the shallows, the tube extended its reach into the ocean. When the lava stopped flowing, it left behind the hollow tube.

Halfway in, we came across an area where the ocean had eroded small holes in the roof. Bright shafts of light streamed in through the gaps, creating a colourful dance against the rock. The walls were a patchwork quilt of orange, yellow and red sponges, a feast for the numerous unusual-looking nudibranchs.

Where the tube curved, striation marks caused by the lava cutting into the outer shell were visible. It felt strange to know that only a couple of hundred years ago, natures ferociousness had thrust the contents of the earths core past the same spot.

After a second dive at the Amphitheatre, we moved to Robs Reef, where we would remain until the next morning. The Kona Aggressor has a diving tender but tends to reserve it for emergency use, so all the diving is off the stern.

While some of the guests said they would have preferred to visit more sites, I found the arrangement agreeable enough. It allowed me more time to explore and revisit areas of interest, rather than spending much of the day in transit.

It also meant that I could plan my diving day to suit myself, instead of having to get into the water at specific times.

For our third dive, we took the opportunity to check out areas that held promise for a night dive.

Once we had completed this task, we set off for the Two Sisters, a pair of caves also formed by volcanic activity. They are entered through two arches that lead into a vast cave, which then splits into two tunnels.

We chose one at random and at its end found what we were looking for - the unusual and endemic ghost shrimp.

The ghost shrimp grows to the size of a small hand, and is mostly white, with a streak of red that runs down its body. What was most noticeable about this unusual creature was its several antennae, twice as long as its body.

As it never leaves the cave, and spends its life in a world of darkness, these are necessary adaptations.

After spending several minutes watching and photographing these creatures, we left the cave. We had found what we were looking for - even the whitetip reef sharks we saw in the distance paled against the discovery of the ghost shrimps.

If seeking out unusual marine life during a dive is not your thing, diving off the Kona coastline might not suit you.

There are numerous bizarre and unique species of marine life to be found here. It seems that no less than a quarter of all the species are endemic.

What you wont see are colourful corals and sponges. On Robs Reef, and on all the other sites we visited that week, we seemed to come across the same three or four types of plain-looking yellow and white corals.

The volcanic formations are fascinating but the growth on them isnt. Its only the bright colours of the resident fish that make the background look appealing.

The goal for the night dive was to seek out unusual inhabitants of these plain-looking reefs. We searched the seabed for one of the more surreal members of the eel family, and after several minutes were rewarded with the discovery of a sand-dwelling crocodile eel.

With only a couple of centimetres of head protruding from the sand, we were lucky to find it - what gave it away were its bright red eyes and large mouth. This eel lies motionless in the sand as it waits patiently for unsuspecting prey to pass by. Even our presence didnt make it flinch.

On the reef we came across the Hawaiian white-spotted toby, with its distinctive green eyes and white spots, and a little spotted boxfish, with its black markings.

These normally shy fish were easy to find in the darkness, despite being no more than 3 or 4cm long.

As I continued to scan the reef, my torchlight caught a flash of silver. Moving in closer, I saw a miniscule juvenile toby sitting on top of a piece of coral. Its eyes and mouth took up most of its tiny, silvery body. Like all creatures with big eyes and a cute face, it had me transfixed for several minutes - it was the perfect photo opportunity to mark the end of the dive.

The rest of the week presented us with a range of volcanic sites where we came across more examples of unusual marine life: the Hawaiian turkeyfish (a bit like a lionfish); the ugly 60cm-long titan scorpionfish and a vast range of butterflyfish and angelfish endemic to Hawaii.

Some of the sites could best be described as interesting as opposed to exciting, while a few were simply breathtaking, the most spectacular being AuAu crater.

At this site, the Aggressor moors so that its stern is directly over one side of the crater walls. The crater drops off to a depth of more than 60m, and then into the open ocean.

We fell directly into the craters mouth and finned over to the other side where, in deeper water, we caught a glimpse of several whitetip reef sharks. To provide some colour, the dark volcanic walls were punctuated by delicate strands of wire coral and large ribbons of nudibranch eggs.

The wall on its own wasnt too fascinating, but as I hovered in the centre of the crater, I felt as if I was in the Grand Canyon of all dive sites. Thats the attraction of AuAu crater.

Our final nights diving and the manta experience soon caught up with us. We resigned ourselves to the fact that things couldnt really get any better. We had one more dive left the next day and it didnt get any better - but it came close.

Turtle Pinnacle is precisely what its name suggests, a shallow plateau where more than 20 normally shy turtles hang out while theyre pecked at by hundreds of cleanerfish. Its the turtle equivalent of Stingray City, only more sedate.

After 20 minutes of watching turtles, we decided to move on to the surrounding reef. It was here that an inquisitive turtle discovered us. We tried our best not to annoy it or get in its way, but wherever we went, it followed.

How it became so tame, I dont know. Had it become used to being fed by visiting divers One look at its powerful jaws put me off that idea. Perhaps it was as fascinated by us as we were by it. It certainly put the icing on the cake for our last dive.

Is the Kona Aggressor II worth travelling halfway around the world for While the lack of invertebrate diversity might not be for everyone, what Hawaii does have to offer are diving moments that simply refuse to be ordinary: the underwater volcanic formations; the unusual endemic marine life; the turtles and the mantas.

We didnt see any whales and dolphins, but we were assured that they are often seen on dives.

If you go all this way, you might well want to spend extra time onshore on the Big Island, where there is plenty to do: visit the Volcanoes National Park and its active lava flows; play golf, enjoy the incredible beaches and perhaps do some more diving.

If youre looking for a break from the familiarity of the Red Sea or the Caribbeans colourful reefs, Hawaii might be what youre looking for.

Entering the Two Sisters - twin arches that lead into a huge cave and two tunnels
only the head of this crocodile eel is visible
ghost shrimp at Two Sisters
a titan scorpionfish
a miniscule toby
Inquisitive turtle shows uncharacteristic level of interest in Brendan O'Brien
Yellow trumpetfish
The stern of the Kona Aggressor II, showing its spacious sun deck and dive platform


GETTING THERE The journey from the UK to the Big Island requires an overnight stop in Honolulu or Los Angeles. The journey back can be done without a break, but Hawaii is exactly halfway around the world and Brendan OBriens return trip involved four tiring redeye flights.

DIVING: Harlequin can arrange diving with flights and transfers, starting at£2035 for one week.

ACCOMMODATION: Kona Aggressor II is a 25m aluminium catamaran, so it is stable in rough seas. Each of the five staterooms has a double and a single bed, large window and en suite facilities, and opens onto a lounge with ample room for the maximum 10 guests. The upper deck has a sundeck, hot tub, open bar and grill. The large diving platform has two entry points, with generous storage space and camera table. Food is first-class, with a diverse menu - all food and alcoholic drinks are included in the price. There is E-6 processing and a range of rental Nikonos camera equipment. Nitrox is available and rebreather units for hire. The vessel is disabled diver-accessible. Harlequin can also arrange accommodation for extra nights on the Big Island if required.

FURTHER INFORMATION Contact Harlequin on 01708 850330. Kona Aggressor II details are on www.aggressor.com or call 504 385 2628 (USA) or 808 329 8182 (Hawaii).