Nudibranchs - those brightly coloured sea slugs that remind you of coloured popcorn - don’t live very long, so a species that is abundant one month may be difficult to find the next. It helps to know who is seeing what and where so you can be on the look out for new, exciting, rare or different species.

Here is an update on nudibranchs at the Poor Knights Islands. It's not meant to be an exhaustive list; the islands are huge and the range of nudibranch habitats is extensive. This is my summary of what I was excited to see during the month of August.

If bigger is better then New Zealand is really delivering the goods right now. Forget those teeny tots from the tropics, we grow our nudibranchs cigar-sized.

There have been regular sightings of the Gem Nudibranch (Dendrodoris denisoni) with its pale brown protuberances and brilliant blue spots, the velvety Verco’s Tambja (Tambja verconis) and the gloomy light-sucking Morose Tambja (Tambja morosa) with its electric blue highlights. No magnifying glass required to spot these monsters.

If you’ve never had the patience to wall gaze long enough to find a nudibranch the size of your little finger nail, then these beauties are for you. Don’t get overconfident though, surprisingly the raucous mustard golds and electric blues of these sea slugs are great camouflage on the bright bryozoan-colonised walls that are typical of the Poor Knights Islands at this time of year. That being said, if you can’t spot one or two of these chunky beasts then you may as well give up now and go wreck diving.

Dare I say that we are experiencing a plague of the Fine-lined Tambja (Tambja tenuilineata) right now? The walls of Middle Arch are alive with these mid-sized nudis. Look out for the interesting variant of this species that is displaying a pale green to yellow colouration with diminished stripes.

Take out your underwater light and wait for the sun to descend, a night dive will introduce you to an entirely different catalogue of nudibranchs. The White-lined Cratena (Cratena lineata) has colonised the boulder area around the outside of Bernie’s Cave and Middle Arch at around 16 metres.

Perhaps notable for its absence was one of my favourites, the flaming Red Janolus (Janolus ignus) - or as my autocorrect is trying to insist, the Red Jangles. I did spot one confused cluster of Blue Janolus (Janolus mokohinau). After dark seems to be the best time to pursue these two species but I had little luck this month.

In other mollusc news - hoards of small squid (<10 centimetres) were encountered while night diving around Middle Arch. They were playing an alarming game of charge and dash. From the black void they would rush my light, halt, splay their tentacles and reverse just as suddenly. The rapidity of their advances was fright inducing; avoid these miniature but bolshy squid if you have a weak heart.

Discovered on Magic Wall during the day, a nudibranch that I had not met before. Tiny (<10 millimetres), obscure, the Brown Trapania (Trapania brunnea) is doing absolutely nothing to stand out from the crowd. If you have impaired eyesight, don’t even try to find this little bugger. If you’re up for a challenge, this is one to look out for.

Not to be confused for a nudibranch, a mistake that I’ve made before (all nudibranchs are sea slugs but not all sea slugs are nudibranchs), the entrance to the Lost World (Jan’s Tunnel) is housing the sap-sucking slug Blue-spotted Elysia (Elysia sp.), and a delicate white flatworm. I’ll need to return with a macro lens to capture these guys.

We are now experiencing our winter low water temperatures around the country (~14 degrees Celsius in northern New Zealand). Nudibranch populations are booming so whack on an extra layer of neoprene or thermal undergarment and head out scuba diving to hunt down your favourite mollusc.

Pucker up! Signing off with a kiss from Bordered Roboastra (Roboastra luteolineata).

Thanks to Dr Richard Willan, Senior Curator of Molluscs at the Museum and Art Gallery of the Northern Territory in Australia, for his ongoing support and help identifying the molluscs I find.

Have you seen any nudibranchs in New Zealand lately? Please share by making a comment below.

Sunk as a wreck for scuba divers in 2007, the ex-HMNZS Canterbury has since become an artificial reef within the Bay of Islands. Colonies of Corynactis australis (Jewel Anemones) have propagated along the railings around the wreck and on the hull itself.

In 2009 divers from Northland Dive descended on the wreck. By accident they discovered a great natural phenomenon of New Zealand's underwater world.

Corynactis australis are known for their high degree of colour variability. In addition to spawning they also reproduce by fission. Their bodies split in half vertically, forming patches of similarly coloured individuals.

Paul Caiger's discovery of Ercolania boodleae in New Zealand has been published in Sportdiving Magazine.

Willan, R.C., Perkins, A.J. & Caiger, P.E. (2015). Boodlea baffles biologists. Sportdiving Magazine 169: 74-76.

The article has been sent to Professor Hamish Spencer for incorporation into the Checklist of the Recent Mollusca Recorded from the New Zealand Exclusive Economic Zone (http://www.molluscs.otago.ac.nz).

The article has also been sent to Lisa Marie, Incursion Investigator with the Ministry for Primary Industries (MPI). MPI is interested in any new-to-New Zealand species - plant, animal or disease. They have staff on duty 24/7 for terrestrial and marine reports. If you ever find a new critter or witness a mass mortality event (e.g. fish stranding), phone MPI on 0800 80 99 66. MPI are happy to check things out and have laboratory facilities for investigating suspected diseases. We don't need any more pests in our marine space.

A risk assessment will be performed on Ercolania boodleae to determine if there is any threat to our environment. Many thanks to Lisa from the Surveillance and Incursion Investigation (Animals and Marine) Team, it's great to know they've got our back.

I'm thrilled that this story has had a happy ending. For a while it looked like finding a place to publish this discovery would allude us and we would have no official record. Dr Richard Willan has done a fantastic job writing up this discovery and securing publication in Sportdiving Magazine. Thank you Richard and Paul!

Winners of the 2014 New Zealand Geographic Photographer of the Year competition were announced at a gala event on Auckland’s waterfront last night. The evening was a culmination to the sixth annual exhibition of the photographic finalists and was celebrated with food, drinks and live music before a presentation of the winners.

Guest speaker and ambassador for Nikon Chris McLennan wowed the audience with an impressive collection of wildlife and landscape images from Svalbard, Alaska and Africa, and those were just his shots taken this year. For those of you who aren’t familiar with the work of kiwi Chris McLennan, who hails from the Queenstown area, you can easily lose yourself for an afternoon on his website.

Presenting the winners of the competition, James Frankham, editor of New Zealand Geographic magazine, commented that the winning photographs were chosen from among the 3400 entries because they captured their subjects in an original and insightful way; they were unique and universally engaging.

The underwater picture of a small jewel anemone captured in the throes of love-making and broadcast to the world (thank goodness you don’t need a model release from an invertebrate!) walked away with two awards from the event: a highly commended in the wildlife category and winner of the Colour Award from sponsor Resene.

One of the competition judges Arno Gasteiger made the general comment, “luck favours the prepared”.

“Who won the People’s Choice Award” I can hear you screaming? 36,000 people voted and the people have spoken. The champion was Kelly Wilson’s photograph of the Kaimanawa horses, a population of feral horses in New Zealand descended from domestic horses released in the nineteenth and twentieth centuries. Each year the horses are mustered to control herd numbers and horses that can’t be re-homed are slaughtered. The Wilson sisters Kelly, Vicki and Amanda have been working hard to place the horses in homes.

In breaking news James Frankham announced a new category for the 2015 competition, which will open for entries in May: time-lapse. We have been instructed to work out what an intervalometer is, but more importantly for me – do they work underwater?!

To see all the category winners from the competition visit the New Zealand Geographic website. Or pick up the November/December issue of the magazine, in stores November 3rd.

This has been an exciting experience for me and I want to personally thank Julia and Shane from Northland Dive who always take me out on amazing scuba dives and who shared with me the very special anemone-spawning event. I also want to thank my family and many wonderful friends who are openly critical of my photographs when appropriate and from who the warm wishes have been flooding in. Your support means the world to me.

Death by lemon shark - it would make an interesting tombstone.

Scuba diving at night with sharks; it's exhilarating, or the stuff of nightmares depending on your point of view. Enveloped by inky blackness as the sun steers below the sea, the water gets thicker, the sharks move faster and it's hard to see them coming. So it seems.

For an underwater photographer fascinated by sharks - it's the best and the worst. Flashes of velvet white belly against a silk curtain of jet-black; there must be some great pictures there for the taking: if you can get a focus lock on your camera in the low light, if you can see your subject coming, if your model and its toothy grimace aren't crash landing at your feet in a cloud of silt.

Mid-water, at speed, a lemon shark is bearing down on me. It's a robust, medium shark with a generous girth. A shark of this size doesn't make you think about being cautious, survival instinct means you are. Something doesn't feel right. I have been approached by lemon sharks. They look like rotund grey hovercrafts suspended a couple of inches off the sand. This one looks like a barreling train, and its monorail leads right to my head.

I'm convinced collision is imminent. Momentary panic. Heart racing. Is this shark really going to hit me? Without warning, like a plane mysteriously shot from the sky, the shark flips belly up, dives and crashes nose first into the sand.

I fired off one shot.

It was vexing behaviour. I'm not a marine biologist, I can only speculate. Driven mad by a parasitic itch? They’re so hard to scratch when you don’t have hands. Looking to shake off the relentless swarm of remoras around its head? It was a passing shark, I didn't ask it. I slumped back astonished. Then swam off, inspired for more harmless night diving encounters with sharks.