Poor Knights marine reserve
Knight's nights, where to night-dive and what to see
by Dr J Floor Anthoni (2007)
Diving at night or nightdiving as it is called, is one of the most exciting things one can do underwater, or even when snorkelling or free diving. Because the blue daylight is no longer there, colours become more vivid in the light of the diver's torch. Fish sleep and become more approachable, while an entirely new guild, that of the nocturnal animals, the night shift, comes out in the open. The Poor Knights with its capricious sea scapes provide some of the world's most spectacular opportunities for doing a night dive.
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What is required for a night dive?
Why is not every spot at the Poor Knights suitable for night diving? Let's face it, diving by night adds new difficulties like being disorientated, not being able to see far, either under water or above, losing sight of the charter boat, becoming separated from the buddy, not being at ease because of fear for the unknown and for what one cannot see, not being able to read the gauges easily, and so on. It follows that night diving is not as safe as day diving, and that it requires new skills.
In the ideal situation, one would do a day dive on the night dive spot first, to become familiar with the terrain, and this should remain a rule of safety. In case this is not possible, one expects an extensive briefing about the lay of the land, depth of the anchor, compass orientation, currents and so on. Above everything else, a night dive spot should be chosen for its safety and this rules out excessive depth, currents, waves and a confusing lay of the land. So here is to consider point by point: Having said all that, night diving does not need to be more stressful than day diving. For myself, it is just another dive, but a very enjoyable and productive one. The next chapter explains why.

What are the best spots for nightdiving at the Poor Knights?
night dive map Poor KnightsThose who studied the best spots for snorkelling, will no doubt notice that those same spots are also best for night diving, but there are a few more:
  • Barren Arch: in conditions of calm at the east coast, Barren Arch is an ideal place for overnighting. With the boat stationary, and a day dive preceding the night dive, a good night dive can be had. But the lay of the land can be confusing at night. The northern cove, which is also the most shallow, is where the boat will anchor, and from here a good night dive can be had, even over the rocky bottom and along the walls there. The arch can not always be entered from the shallow side, and one needs to find it, going around the outside to the deep end, and back again, which takes precious time.
  • Rocklilly Bay: surprisingly, a good night dive can be had on its northern side which is sheltered from NE swell and storms. The beautiful rock life begins a little deeper than on the west coast, but between 10 and 15m a very colourful community can be found.
  • Middle Arch: we give Northern Arch a miss because of its unpredictable currents and very deep bottom, but for experienced divers it can still be done in favourable conditions. By comparison, Middle Arch is much safer, and also more interesting for night diving as it has more habitats closer together. It is a very colourful dive with astounding sessile life in shallow water.
  • Butterfish Cove and Maomao Arch: although the bottom is 40m deep, the walls are tranquil and rich in life. Watch out for currents in Maomao Arch. There are large boulders in the cove, tall seaweeds outside, and here and there a small cave.
  • Skull Bay: a very sheltered bay which does not receive much sunlight during the day. As a result, a reasonably good dive can be had in the kelp forest with sleeping fish, and along its steep but shallow walls. It is an entirely safe place.
  • The Canyon: the boat anchors on a knoll, away from the shore and divers descend along this knoll, and into the narrow canyon. This dive is tricky because some divers have to find the anchor chain on their return.
  • Dog-leg Channel: a safe and colourful night dive along the walls of the island. The sandy bottom is not deep.
  • Nursery Cove and the Labyrinth: always astounding, although not colourful. A great variety of habitat and fish. A visit to The Labyrinth goes over sand, along a steep wall and through a small archway with colourful gorgonean fans and sponges.
  • The Gardens: plenty of opportunity for shallow night dives, from El Torito Cave to Trev's Rock. Not colourful and not very varied either.
  • Jan's Tunnel: an astounding night dive because of a jagged bottom contour with passages, and untold many sleeping fishes. Deeper down one also finds a colourful community.
  • Ngaio Rock: like Jan's Tunnel but not very colourful.
  • Blue Maomao Arch: one of the best night dives, both inside the very colourful archway and outside. Most sessile life is found on its eastern entrance.
My choice: 1. Middle Arch, 2. Blue Maomao Arch, 3. Nursery Cove and Labyrinth, 4. Rocklilly Bay.

The night shift
Night dives are extraordinarily satisfying because of what they offer:
  • sleeping fish: one can see how fish sleep and how they change colour, sometimes being almost unrecognisable. But some sleeping fish hide so well that they cannot be found. Wrasses like Sandager's wrasse for instance, burrow in coarse sand under overhangs, the dominant male last. Sleeping fish can often be approached easily, and at times even be handled.
  • animals that come out only by night: many animals are nocturnal, hiding in deep crevices or under stones by day. During the night they suddenly appear, often oblivious to the diver's torch. Molluscs need their time and usually appear later in the evening. It thus pays to do late night dives now and then.
  • colour: because the blue light is absent, the underwater world looks very colourful, almost too good to be true.
scarlet wrassse (Pseudolabrus miles) sleeping in sponge
f028914: a scarlet wrasse (Pseudolabrus miles) has made himself a cozy bedroom inside a grey sponge. By rubbing the opening, it prevents the sponge from closing up. Notice the white margin of damage to the sponge.
scarlet wrassse (Pseudolabrus miles) in pyjamas
f041720: many fish don pyjamas at night, assuming colour patterns that are at odds with their daily colours. Here is a mature scarlet wrasse, now pink instead of red, and its white belly coloured the same as its back.
pink maomao (Caprodon longimanus) in pyjamas
f043321: pink maomao (Caprodon longimanus) don almost red pyjamas which change with age. This fish is very old.
butterfly perche (Caesioperca lepidoptera) in pyjamas
f048408: butterfly perches (Caesioperca lepidoptera) are light orange-pink by day but dark brown by night.
baby leatherjacket (Parika scaber)
f043314: this is a 5 cm baby leatherjacket (Parika scaber), woken up from its sleep and ill at rest. These fish sleep while biting on to a kelp leaf or other hold-fast.
young leatherjacket (Parika scaber)
f043312: a young leatherjacket, blinded by the light and still ill at ease, allows itself to be handled. Notice the scatter caused by zoo plankton.
male two-spot demoiselle in pyjamas
f012535: a male two-spot demoiselle has turned its white spots off completely, assuming an almost black colour.
female two-spot demoiselle in pyjamas
f009816: this female two-spot demoiselle has become green-black, and has almost turned her white spots off.
big-eye (Pempheris adspersa)
f048419: big-eyes (Pempheris adspersa) hide inside caves and crevices by day, to come out at night. With their sensitive eyes they are able to catch fast swimming bugs in the scant light of the moon. For this reason they are found in the shallows only. They never sleep.
slender roughy (Optivus elongatus)
f041430: the slender roughy (Optivus elongatus) is like the big-eye a nocturnal planktivore, hunting and hiding in the same places as the big-eyes.
toadstool grouper (Trachypoma macracanthus)
f051403: toadstool groupers (Trachypoma macracanthus) belong in warmer subtropical waters. They hunt in the weak light of dawn and dusk.
triangle crab (Eurynolambrus australis)
f036414: a triangle crab (Eurynolambrus australis) hides underneath boulders by day, but forages at night.
fire slug (Janolus ignis)
f037905: the fire slug (Janolus ignis) comes out late in the evening.
f051430: this unidentified flatworm comes out late in the evening.

Tips for photographers
For underwater photographers, the night dive provides an inexhaustible supply of opportunities, but there is a problem. During the night, free swimming plankton organisms become attracted to the diver's torch or the photographer's 'modelling light' atop his strobe. This invites them right into the very area of the frame where backscatter is worst. Twice already I have had to abandon a night dive because of this. 
The kind of creatures causing this problem are many: tiny copepods buzzing around like golden fleas, swimming shrimps (krill) of various sizes and fast swimming bristle worms.

Here are tips to minimise this problem:

fast swimming shrimps at night
f045521: fast swimming shrimps like these can destroy your night dive. In fact, it was this night dive that I had to abort. There were sea lice too that kept biting my hands.
divers should have bright torches
f025019: a bright torch with flooding light is your best tool for night diving. The light shown here is 50 Watt, connected by cable to a 12V 6Ah battery pack on the dive tank.

The diver's torch
Most dive torches sold in dive shops are useless for nightdiving. Divers are sold little toys good enough for reading gauges by, and even for this they are inadequate. What you need is not a spot light that concentrates all light in a little spot, and then blinds your eyes, but a flood light of at least 20 degrees. Also the minimum light power is 10 Watt quartz-halogen.
Being an underwater cinematographer, I have been spoilt rotten since my very first dives, by carrying a 50W (car head light strength) light source, connected by cable to a battery pack attached to the dive tank. I later perfected the techniques for making my own tiny but powerful dive lights (to be disclosed in the section on underwater photography). Do not use torches running on AA batteries, but buy one on DD batteries, or at least CC batteries. Check that the chromium reflector is pitted and that it casts a flood light rather than a spot light. The latest developments on bright white LED lights (Light Emitting Diodes), looks very promising, in which case AA batteries might just suffice. Remember that night diving is all about pleasure and amazement, and that an inadequate torch can spoil it all.

Your most important night-dive tool is your torch! Don't skimp on it!