WHEN YOU TALK to divers from all over the world about dive sites in Australia, they will most likely start a conversation about the Great Barrier Reef, and in very rare circumstances, if you’re lucky, they might mention Tasmania’s east coast. And talk to a local Tasmanian diver about their favourite dive sites, and you will probably get into a conversation about the best sites to catch crayfish or abalone (if they trust you), or you might hear about disappearing kelp forests and the best spots to observe weedy seadragons. But what you will hardly ever hear about are the mysteries of reefs that line Tasmania’s coast below depths accessible to recreational divers…
The reason for this is quite simple – there are maybe a handful of rebreather divers in the state, there is hardly any trimix available unless you mix your own, and the weather is, shall we say, “highly variable”. As a consequence, apart from a handful of dives to the famous wreck of the iron steamship Tasman in 70 metres, the ocean around Tasmania below 60 metres has only been sporadically visited by autonomous underwater vehicles (AUVs) used for marine science, which generally just bring back poor quality video footage. A mostly “undiscovered” underwater world… what better excuse is there to go for a deep dive and have a look?
PLOTTING AN ADVENTURE
Luckily my dive buddy James Parkinson’s friend Neville Barrett, who works as a scientist on the biodiversity and ecology of local reef systems, is heavily involved in producing high-resolution maps of ocean bathymetry around the Tasmanian coast. Using these maps we put together a list of several interesting locations we’d like to dive, including some potential reefs extending from the shallows to more than 100 metres.
With this “wish list of dive sites”, now we just had to be patient and wait for the right conditions to head out onto the water – something easier said than done when you live in Tasmania with the Southern Ocean just around the corner.
So, most weekends we get our rebreathers ready, fill scrubbers, top up oxygen and diluent tanks, check bailout tanks, drive the club boat to the boat ramp, and hope that the weather gods are feeling generous.
Nevertheless, more often than not the weather gods are instead way too excitable, and throw everything they’ve got at us, forcing us to go with Plan B and dive somewhere closer to shore and sheltered by Tasmania’s famous sea cliffs.
But sometimes you can get lucky – really lucky – like the day we planned to head around 10 kilometres offshore from Bicheno on Tasmania’s east coast, to dive a place known to fishermen as “Joe’s Reef”.
From Neville’s high-resolution bathymetry maps we knew that the reef was about 200 metres in length, and comes up from a sandy bottom at around 80 metres, to 58 metres at its shallowest point.
The AUV footage from this reef is quite poor, but it looked like there was some interesting life around. In addition, this site is well known to fishermen, which is generally a good sign. Before the allocated weekend, we topped up the oxygen and 16/50 trimix in our rebreathers, checked the state of our bailout tanks (we both carry two 11-litre tanks, one with trimix and one with 50-percent nitrox) and made a dive plan for a bottom time of 25 minutes and a runtime of 75 minutes.
THE GODS ARE SMILING
On the day of the dive we were woken up by great weather, and looking out towards the open ocean we could see that the ocean surface was amazingly calm. Full of optimism, we put the club boat into the water and headed towards the GPS coordinates of Joe’s Reef.
Once at the site we dropped the shot line, which landed as planned on the shallowest spot at about 58 metres, and deployed the decompression bar next to it. Finally, it was time to jump into the blue and find out what lies in Tasmania’s deeper waters. This was going to be James’ and my first dive in Tasmania to those depths, and we really knew very little about what to expect. The only thing we did know was that on most of the local dives we had done recently, the local reef life becomes much more colourful and exciting the deeper you go (and, thanks to the helium, it wasn’t just the narcosis!).
Once in the water we dropped along the shot line, with visibility improving as we went. As we approached the bottom what we saw can only be described as an overdose of goodness!
The first thing we realised was that we had landed in a garden full of black corals, some more than a metre tall, sparkling with their amazing bright white colour (the name black coral comes from their dark central skeleton as I learned later, but their living tissue can be a range of colours).