It's not terribly easy to reach Nabucco Island. We flew from Singapore on the tip of the Malay Peninsular to the largest city on Kalimantan Timur – the Indonesian part of Eastern Borneo – Balikpapan. Here we spent a night before flying up north to the town of Tanjung Redeb.

The air was strangely hazy but this wasn't a weather phenomenon but rather the result of farmers' slash-and-burn method. The jungle is chopped down and set on fire to give way to a small plot of farmland with just enough nutrients to keep a family going for a couple of years. Then they move on. Apparently the haze wasn't so bad as some five years ago but bad enough to keep the airports of Central Kalimantan closed due to poor visibility. Cars had their head lights on and in some places the visibility was down to 50 metres.

On our flight to Tanjung Redeb we could see tiny smoke columns rise to the sky. Fortunately, when we arrived at Tanjung Redeb it wasn't raining. The runway is so short that planes are only able to land in dry weather and the pilot has to almost stand on the brakes to avoid hitting the banana palm trees at the end of the runway. If it rains the plane would merely continue past the runway.

We were picked up at the airport and driven down to the Berau River where a small motorboat with two crew members waited for us. Our bags and equipment were stowed on board together with salad oil, eggs, butter, mineral water and other articles – supplies needed on Nabucco Island. Soon we headed down river. After an hour or so the landscape flattened as we reached the river delta and the mangroves. Pretty soon we were out on the open ocean and couldn't see land at all.

Yet another hour passed and a small island emerged on the horizon. Naturally, we thought it was our dive destination but no. Not until after three hours of sailing did we arrive at Nabucco Island. The voyage could have lasted longer but we only had three engine failures on the way and the weather was nice – a bit overcast but no wind, fortunately.

Nabucco Island was named after Verdi's Gefangenenchor aus Nabucco as performed by the Hebrew slaves. The island proper is doesn’t take up more than an area of 20,000 m2 at the most. It lies like a small dot below the eastern end of the Maratua atoll some 90 km from the mainland of Borneo.

We were warmly greeted by co-owner and manager Walther with freshly cut coconuts and he told us of the islands many splendours. It was Walther himself who found the spot for the dive resort. A couple of years before Walter did some diving on the surrounding coral reefs but was taken by the current. He more or less washed ashore on this small island, took a quick look and thought to himself: This is perfect for a dive resort.

And it was a perfect dive resort. Quality materials and design, hot water from solar energy, nice and spacious twin cabins – all with own porch facing the sea, big bathrooms and a big hall with plenty of room for a diver's luggage. Not a single palm tree had been chopped down to give space for any construction on the island. The distance from the farthest of the twelve cabins to the jetty and the restaurant was some 100 m. Nowadays it seems that six twin cabins have been added – all with air conditioning.

The quality of resort was underlined by the Nabucco chef, who seemed to produce wonders in his kitchen. Most of what we were served had a western flavour with local touches but it was very varied and tasteful. At breakfast we dug into omelettes, pancakes, toast, fruit and freshly baked bread. Each night – except on barbeque nights – dinner consisted of four delicious courses: A soup, a salad, the main course and finally dessert. And, of course, freshly baked bread again.

No matter how hard, how long and how often we dove, we didn't loose any weight. For lunch we usually ordered a tasty sandwich and some fruit to bring along on the dive trip, though temperatures at some 40 degrees around noon usually did away with any immediate hunger.

Some of the guests at Nabucco were expats who simply came for a few days to relax and reload before returning to the timber and oil industries on the mainland. They didn't even dive!!! But the atmosphere on the resort and among the staff was inviting indeed and did warrant such silly behaviour.

At the time of our visit Nabucco had functioned as a dive resort for eighteen months and had two Indonesian dive guides, both PADI Divemasters: One from Jakarta and one from the neighbouring Maratua Island. The resort had two dive boats: One with room for 12 and one with room for six divers. In spite of this only one oxy-box was available but – as we later found out – no-one knew how to operate it, so it didn't really matter.

There's 1½ metres' difference between high and low tide in this area so on almost all our dives we went with the current though on some occasions going against would have been totally impossible. No more than 100-200 metres from Maratuas's east coast the depth plummets to a staggering 2½ kilometres, and four out of five dives were vertical wall dives.

For once our logbooks and certificates were studied thoroughly but other than that the dive guides didn't impress us at all. Briefings were kept to “reef on your right shoulder” or “maximum dive time 60 minutes or 50 bars” whichever came first. If we asked them what to expect from the dive, they didn't reply “to get wet” but they might as well have done just that.

We had an incident where a not that experienced diver went into deco after a hectic dive at Barracuda Point at Kakaban Island. The chaos that followed is almost indescribable. As the deco diver apparently couldn't read his own dive computer someone on our boat calculated – without checking with the unfortunate diver – how long he was to remain at five metres. Don't ask me how. A couple of other divers started to shift dive gear from the big boat to the small boat as they wanted the big boat to quickly get the deco diver back to the resort. They hadn't considered that putting 12 fully equipped divers on the small 6 seater boat through a rough sea might present a far worse scenario.

The guides? They went on a hike on Kakaban Island, the boat crew sat cosily at the rear of the big boat and chatted, and the one person that perhaps should have reacted and calmed everybody down – a German CMAS instructor – didn't do anything at all. So it fell to us to put a lid on the situation as best we could. The crew couldn't find the oxy-box let alone assemble it so we started by doing that. And then after some heavy discussion we managed to stop the two divers from shifting gear. When the unfortunate deco diver surfaced a quick glance at his computer revealed that he seemingly was okay but perhaps should skip tomorrow's dives just to be on the safe side. And then he happily emptied the oxygen bottle.

In all fairness, the resort has changed dive guides since then and hired a professional instructor to sort out the safety issues. But it does go to show that conservative diving well within the limits is a must – especially when you're stuck on a rocky outcrop eight hours by low-flying helicopter away from the nearest recompression chamber. All our dives were fairly deep and demanding, and with a temperature of 40 degrees in the shade dehydration and possibly the bends were a very real possibility.

In spite of alluring dive site names we saw no turtles at Turtle Parade, no leopard (zebra) sharks at Leo's Point and no barracudas at Barracuda Point. But according to the guides we were just unlucky. We did find a striking absence of fish of more than 10 cm or so.

Most schools were small bass at the reef tops, and along the walls we now again bumped into squirrelfish, angelfish and parrotfish. On the other hand, the reefs seemed absolutely crowded with scorpionfish. Some were camouflaged beyond recognition, others flashed bright and radiant colours and still others had adapted the most delicate pastel shades. Really beautiful and spectacular.

Nudibranchs were the order of every dive and we often found “new” species, i.e. slugs we hadn't seen before. It seemed that the dominant species was Chromodoris elizabethina but we managed to run into C. willani as well. Also the very large variety in hard corals was impressive.

As previously mentioned high and low tide in this area differs by 1½ metres so we went with the current on most dives though on some occasions going against would have been totally impossible. No more than 100-200 metres from Maratuas's east coast the depth plummets to a staggering 2½ kilometres, and four out of five dives were vertical wall dives.

From a narrow perspective Nabucco Island's main attraction is Nacha as the locals call it, which translates into something like Big Fish Country.

At Nacha/Big Fish Country you dive down to about 26 metres – preferably at the height of the tidal current in the early morning – along the eastern wall of the Maratua atoll just in front of a deep entrance into the atoll and then hang on for dear life – waiting for stuff to happen.

After the first dive we complained at length because people were hanging on to corals of all shapes and sizes. We were then issued a hook so we could easily “fasten” ourselves to rocks and the like. But the rewards were great though: Zebra sharks, white tip reef sharks, grey reef sharks, spotted eagle rays, tuna and the greatest school of barracudas we had ever seen.

Our dive guide Medi knew a thing or two about attracting barracudas – at least that was what he claimed. On one of our dives he kept swirling his hook round and round and round. The blue horizon got darker and darker and little by little it grew into a veritable tornado of barracudas. The top of the school almost touched the surface and the bottom seemed to loose itself in the depths. Barracudas were everywhere.

We left our safe haven at the edge of the reef and slowly dove towards the school. It was totally unreal to hover but one meter from a wall of barracudas that almost didn't care to move for a pair of tin cans like us. It was just so impressive when the silvery predators slid into a formation of a horizontal figure of 8 where we could see the school almost in 3D.

Of course, this dive was widely discussed afterwards. Minimum bid was about 2,000 torpedo shaped predators.

Before we had our first dive at Big Fish Country we were warned not to bring the uw video camera as our guide thought the currents would make it impossible to hold still and, more seriously, it could constitute a safety hazard. Of course, we obeyed though seen in the rear-view mirror we must admit that if you've experienced (and survived) the sounds and belts of Denmark on one of their more disobliging days you are reasonable well prepared for whatever hardship other of the world's dive spots may have in store for you.

We had a super dive at any rate: Six white tips and a grey reef shark, a couple of big tunas, a large whitespotted eagle ray and a small school of barracudas. Lene had positioned herself at the far end of the group and became just a tiny bit nervous when one of the large white tips took a particular interest in her – so she thought, anyway.

The rest of us just rejoiced in this spectacle as the shark even in spite of the stiff tidal current effortlessly swam back and forth to have a closer look at us. I did get a sense of Lene's state of mind as she came hopping along the rocky edge and settled down within arm's reach.

We spent a lot of time at Big Fish Country :-)

Sangalaki is a small bounty island to the west of Maratua. There used to be a dive resort but it is now closed, and the island has been turned into the Kepulauan Sangalaki Marine Wildlife Reserve due to the large amount of green turtles that use the white sandy beaches to lay their eggs.

The currents around Sangalaki apparently concentrate plankton and small crustaceans to the extent that the waters become a genuine larder for hungry manta rays – all year round according to everybody we asked. When we probed a bit the locals did admit that there had been a three months' period four years ago when the mantas suddenly disappeared. That would have been in 1998, and a fair guess would be that El Niño also took his toll here like so many places in the Indian and Pacific Oceans.

The dive site Manta Cleaning Station has a maximum depth of approx. 15 metres. There is a “runway” of sand surrounded by coral pinnacles and bommies that goes parallel to the current. We didn't fancy getting stuck in table corals or knocking large fans about so our only option was to sit ourselves down on the sandy bottom on the runway with our backs against the current and our heels placed firmly in the sand. It looked silly but it worked.

In this way we slowly but surely slid along the bottom towards to cleaning station. We got really close after a while and saw a couple of huge mantas descend upon a rock and make themselves available to literally every kind of small fish in the neighbourhood. One of the mantas was cleaned inside out by gobies, bannerfish and wrasse.

The best part of the trip, however, came during our lunch break. The dive boat drifted slowly with the current into an area not far from the shore. We could see lots of small tail fins breaking the surface. A quick count led us to believe that we were almost on top of some 40-50 manta rays busy foraging. We very quickly put on suits, masks and snorkels and jumped in.

And there we were. In the middle of what could best be described as a manta ray feeding frenzy. We were at any given time surrounded by at least 6 or 8 mantas. The smaller ones reached some 1.5 metres across the wings and the larger ones about 4-4.5 m. They all kept on filter feeding quite oblivious to our presence, and some of them came so close that their wings brushed against us. Really, really, really awesome.

We got just a teeny-weeny bit paranoid by all those big hungry mouths incessantly coming towards us from all directions. Only at the very last second did they turn away and went either below us or to the left or right of us.

Usually manta rays have black backs and a white bellies. But here we also saw quite large mantas that were totally black. Our dive guide called them Darth Vaders, which seemed like a fair description. In all we managed to get five dives around Sangalaki Island – not forgetting the coolest snorkelling trip ever.

Usually when divers talk about a jellyfish lake, they refer to the jellyfish lake on Palau far out in the Pacific Ocean. The truth be told: The Indonesian archipelago holds numerous lakes like the one on Kakaban Island – quite close to Maratua. And it certainly was an experience.

The pioneers who first dove the lake on Kakaban Island had to endure a long and arduous walk through hilly jungle and across razor-sharp rocks fighting off swarms of thirsty ”blood-sucking flies” in 40 degrees C and an air humidity of 95% - in full scuba, of course. All this for a dive in a salt water lake full of jellyfish, sea cucumbers, crabs, disgusting mangrove (if you ever snorkelled in between mangrove trees, you'll know what I mean) and … oh… a beautiful, indigenous goby and lots of nudibranchs, tunicates, sponges and lots more. A completely isolated, self-serving eco-system.

Of course, all this hassle in a recreational sport won't do, so a local fisherman was hired to make a wooden path from the beach to the lake with stairs and steps and rails and everything. When we visited he had been at it for a couple of years and needed only to cover the last 200 metres in the middle of the path. It still was a sweat-drenching ordeal – for us, that is...

During the last glacial or ice age which ended some 10,000 years ago sea level was about 120-130 metres lower than today. The melting of the ice caps caused a huge sea level rise – higher than today – and an increase in temperature in the Northern Hemisphere until about 5,500 years ago. Then the temperature decreased again and sea level fell to present day level – trapping the poor jellyfish in the lake on Kakaban Island. The name Kakaban actually means “hug” in the local dialect as the island hugs the jellyfish lake from the outside sea. Kakaban is also part of the Kepulauan Sangalaki Marine Wildlife Reserve.

The jellyfish in the lake used to sting but has lost their ability due to a lack of natural predators. And a good thing too, ‘cause we were quite clearly outnumbered – there were thousands of them. One of at least four different species spent most of the time bottom up on the bottom feeding. The other three were all very busy swimming back and forth exposing their built-in algae to the sunlight thus creating photosynthesis.

There seemed to be two dominant fish species though we weren’t able to identify them. Hiding between the roots of the mangrove trees we found a beautiful dark-coloured goby with lots of small blue-green spots down the side.

By the way, the blood-sucking flies turned out to be horse botflies. Their bite still hurts like hell but they don’t carry deceases, and knowing what they are makes the trip from the beach to the lake a little less scary. They should in no way prevent you from doing the trip. Lene and I shared our scuba gear and took turns diving and snorkelling, respectively.

One evening we sat on our porch overlooking the water. We had turned on the porch light and watched in fascination the cornet fish hunting in the shallows.

Suddenly the silence of the dark night was ripped by a horrific moaning and groaning. Instinctively, it sounded like a little child being tormented and just about to expire.

The next morning we asked about but perhaps due to our graphic description nobody seemed to know what we were on about. Until it dawned on one of the locals. It was just the largest bats in the world, the flying foxes, which visited the banana palm trees on the island at night, and quite often came to blows over the food. We were quite relieved.

Our stay at Nabucco Island Resort didn’t provide us with much local colour. In principle we could have been on almost any small island along the equator.

The resort did offer a four hour five dollar excursion to the main island of Maratua, which would lead you through a village, a bit of jungle and a tiny jellyfish lake, and – if you were lucky – you might catch a glimpse of a monkey or two. A couple of visitors did the tour and warned off the rest of us.

After one of our dives we put in at the captain’s home village on Maratua Island to have a look around. The school in the village collected all the kids from the neighbouring islands for elementary school, and quite a large mosque was the haunt for the inhabitants of the district on special occasions.

In some very tall trees we could see our nocturnal flying friends hanging head down patiently awaiting nightfall. Of course, some of the kids had gotten their hands on a bat and proudly displayed it by holding it at each wing tip stretching it to its full wingspan of some 1.5 metres. Really impressive. It looked more dead than alive, though, and had probably fallen out of tree by itself – hopefully.

Anyway, go to Nabucco Island for the diving, not the local colour. Especially, Big Fish Country is quite unique and always in for a pelagic surprise.

Our trips to both Sangalaki and Kakaban were truly once in a lifetime experiences to be relived and revered during dark and cold Danish winter months.