The awesome Taravana Cave

Poor Knights marine reserve
the awesome Taravana Cave
by Dr J Floor Anthoni (2007)
www.seafriends.org.nz/issues/res/pk/taravana.htm

Taravana Cave at the Poor Knights Islands is very large and deep, plunging 150 metres into Tawhiti Rahi Island, connected by a side tunnel, sometimes jokingly called the Rat Hole. Most of the way the diver swims in total darkness at 15-25 metres depth. It is a dangerous dive that could easily end in death.

Where is it and what does it look like? Location of Taravana Cave and sketch of its shape.

Notes from my log book: a personal experience speaks for itself.

Safety precautions: things to consider before waging an attempt.

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map of mid-northern quarter of the Poor Knights

Taravana Cave is found in Butterfish Bay, just north of Maomao Arch.

Where is it and what does it look like?
Taravana Cave can be found in Butterfish Bay, between The Staircase and Maomao Arch on the Poor Knights' northern island Tawhiti Rahi. This part shows a steep dark wall, and where the rock face leans over, is the main entrance. The second entrance, the Rat Hole is found tot he right of it.

A sketch from Floor Anthoni's log book, drawn from memory, 1994

In 1994 I explored Taravana Cave during a well prepared dive. The sketch above shows the situation and what to expect. Taravana's main entrance is very large, between 15 and 32m depth and 20m wide. To the right of it is a 22m deep ledge on which a small boat can anchor with some skill. Note the anchor chain going up to a 5m boat named 'Seasquirt'. In the entrance is 'me', drawn to scale. To the right of this ledge begins the Rat Hole, a much smaller entrance, but still large as caves go. Divers who want to enter this cave must be experienced and not panic easily, as there exists no ascent, once inside. It soon becomes entirely dark, so a good torch is needed. Safety precautions are discussed in the next chapter.

For a quick taste of this majestic cave, begin at the Rat Hole which opens between 20 and 26m. Soon it becomes pitch dark, and after a long swim, you enter the main cave, with on left the faint blue glow of the main entrance. Swimming towards this large halo that eventually becomes the opening of a cave, is a superb experience. Once outside you can finish your deep dive in the shallows along the steep wall.

Doing the main cave is very tricky because it is a very long swim. I estimated 150m, but it could well be 250m. Inexperienced divers who still use a lot of air, won't make it on a single tank. Inside the cave, it is pitch dark, and one must use a compass because one could easily swim in circles inside. The swim is best done in the top of the arch to avoid running out of bottom time. You can easily run out of bottom time because in the dark, not knowing the precise direction to go, time is wasted in zig-zagging and re-tracking. Remember that you have less than 20 minutes at 30m depth! Communicating with your buddy will no doubt add to lost time. You can also easily run out of air if you are not properly balanced and if you are clumsy at swimming efficiently with all the gear.

The bottom of the cave tapers gradually while rising from 32 to 18m depth. Half-way it makes a slight S-bend. The ceiling of the cave is irregular and ends in an irregular dome. The walls are relatively smooth, but with little if any life at all. At the northern side one can find a thin rope strung above the bottom against the northern wall. In case one loses direction, this rope should guide one back to the entrance. The problem is that it runs near the bottom, thus reducing your bottom time.

From Floor Anthoni's log book
It was an eerie feeling being here at 23m depth and being gulped up by the esophagus of this inanimate being. The walls were richly covered in small white and yellow sponges, and inside cracks sat featherstars, extending their arms up to 40cm (!) outward into the motionless cavity, where neither currents nor waves enter.

After about 40m the tunnel of the Rat Hole ended abruptly into an ultra-dark space that proved to be the main tunnel. To my left, only 40m away, the faint blue of a gigantic entrance. The sandy bottom receding to 32m deep and the ceiling abruptly rising to 16m. This was not a cave or a tunnel but a full-blown cathedral, more than 5 storeys tall and 20m wide. It was an enormous space that my 100 Watt dive light could not fill.
While swimming through the centre, I could see neither ceiling, nor walls, nor bottom. So I zigged from left to right and zagged from top to bottom, in order to explore this exceptional geological feature. After about 50m, all sense of light had disappeared. the ceiling suddenly jumped to 12m and a slight bend turned the Cathedral northward.

All my senses worked in overdrive. I was watching my compass in order to be able to reconstruct my way out, the depth in order to measure the size and location of the tunnel, and for my depth profile. I also anxiously watched the decompression meter and used air in order to decide when to turn back. I was breathing calmly and sparingly while my legs kicked a steady beat. "Grog, grog", went the air bubbles inside my suit, with each kick. I could hear my breathing echo loud in this echo chamber, and the exhaled air raced upward and along the ceiling to the highest points it could reach, while making eerie gurgling, running and whistling sounds. I could even hear my heart beat!

At 60m inside the tunnel, I stopped to reflect on what might happen if suddenly the light went out. I turned the light off, and for a moment I was able to read the compass in the dark. Then it faded out. There was no way I could guess what was the way out. I sank to the sandy bottom but it could give me no clues either. I moved towards the northern wall. It seemed to take ages. Was it the northern wall, or the southern wall? I may have swum in circles. Should I swim left to get out, or right? How could I check my air supply? What would happen if the wall had side branches? Would they confuse me? I switched the light on again, and immediately everything looked familiar. But I realised that getting out of this place in the dark would be a major nightmare.

The cathedral gradually narrowed in width and height but it remained impressive. At its very end, my powerful light could not reach all walls from a single point in the middle. Very suddenly came the end. The walls were brown and yellowish with hardly any growth on them, as the water does not get refreshed easily. I swam up to the top at 11m to find dirty brown fresh water!

Back at the main entrance, 32m deep, swam five young john dory. When confronted with my dive light, they became confused and began swimming upside down, thinking that my light came from the surface.

It would be nice if a dive club undertook the accurate mapping of Taravana Cave.

Safety precautions
There are people who insist that you need to have the necessary qualifications such as a cave diving or wreck diving ticket. Others may insist that this cave should be entered only with a full backup team on stand-by, with emergency air supply along the route. Someone may think it is best done alone. This is not for me to judge. But here are some good tips and qualifications before you give it a go.

There is no doubt that this is a dangerous dive, a dive that does not become safer by taking more gear or more people. It is a potential death trap.

You must be able to rely entirely on yourself, because there is little margin to expect your buddy's help. This implies that you can fix equipment problems, switch to alternative air sources and so on in complete darkness.
You must be able to make a 20m dive of one hour on a single dive tank. Taravana is a long swim, easily demanding more air than you have.
You must be comfortable with a compass and have ample experience in how to use it.
You must be comfortable in the pitch dark. There is no place for phobias of whatever kind.
You must have a powerful main torch AND a small emergency torch.

If you belong to a group, make sure that people know what you are going to do. In case you die inside the cave, it takes quite an expedition to find you and bring your body out.