For 15 years Naomi Arrowsmith and her partner Stew have been addicted to diving off Albany on the south coast of Western Australia. 

The diving duo has often found themselves surrounded by schools of tuna and Samson fish. They've swam with giant green turtles, seen reef walls of sea slugs and enjoyed photographing the local corals. 

But one marine encounter was not so welcomed.

Naomi and Stew were swimming in open water after a dive when something hit the electric field of Stewart's shark shield.

"We heard a bang, felt a thump on our chest from a pressure wave in the water, and quickly turned to find all the fish following us had disappeared," Naomi says.

They never saw the shark but a friend fishing in the same area saw a Mako shark in the water.

Naomi had always ribbed her partner for wearing the electronic device but afterwards "went out promptly and purchased a shark shield for myself and ate humble pie for teasing Stewart!"

A love of sea slugs - nudibranchs

Photo above: the beautiful nudibranch Red-netted Chromodoris (Chromodoris tinctoria) was spotted and logged on Redmap by Naomi Arrowsmith close to Albany.

Naomi enjoys hunting for and photographing the small, often-brightly coloured slugs of the sea: nudibranchs (photos she share on Redmap).  

The word "nudibranch" comes from the Latin 'nudus', naked, and the Greek, brankhia, gills.  A suitable name given these marine gastropods, unlike sea snails, shed their shells after the larval stage.

What is left is a soft-bodied creature ranging in size from 4mm to over 30cm that usually crawls over reefs and the seafloor. 

Photo above: an Orange-barred mexichromis (Mexichromis macropus) photographed by Naomi off the coast of Albany and submitted to Redmap. 

Photo above: two Red-blotched Hypselodoris (Hypselodoris sp.) seen by Naomi during a muck dive near Albany. They look like lollies! See the sighting on Redmap.

Finding a cartoon character underwater

One highlight in Naomi's search for local nudibranchs was spotting a Thecacera pacifica on soft corals near Albany (pictured below). This is a special find for two reasons. 

First this sea slug is often referred to as the ‘Pikachu Nudibranch’. 

Its yellow body and black-tipped tentacles bear a striking resemblance to the Japanese cartoon character Pikachu from the Pokemon series (see a photo of Pokemon's Pikachu).

Photo above: the nudibranch Thecacera pacifica is also known as the 'Pikachu Nudibranch' after the Japanese Pokemon cartoon character (Photo: logged on Redmap by Naomi Arrowsmith) 

The sighting is also noteworthy because Thecacera pacifica is not often found in Australia.

According to marine biologist and Redmap verifying scientist David Harasti, from the NSW Department of Primary Industries, the species grows to just 2cm in length and is more at home in warm waters in places like Indonesia.

If diving has become Naomi's hobby so too has photography: she has become a determined and skilled photographer of these small animals.  

Just ask the octopus who tried to steal Naomi's camera - unsuccessfully after a bubbly wrestle!

Check out all of Naomi's colourful sightings on Redmap.