Below the Hippolyte Rocks on the Tasman Peninsula lies a colourful reef full of coral, sponges and fish

Underneath the Hippolyte Rocks on the Tasman Peninsula lies a stunning cold water reef full of sponges, coral and thousands of fish ()

The Hippolyte Rocks are known from shore as the treacherous granite island that rises out of the ocean off the Tasman Peninsula.

The group of rocks have claimed two ships, tricking mariners into passing through the calmer waters between them.

But what lies beneath in the cold water of the Tasman Sea is a colourful wonderland of fish, sponges and coral that rivals the Great Barrier Reef.

Dive instructor, underwater photographer and marine scientist Matt Testoni said Hippolyte Rocks and nearby Trident Reef were the best dive sites in Tasmania.

“I think it’s some of the best deep diving in Australia,” he said.

“I find it much better than the Great Barrier Reef.”

The reefs are part of the Great Southern Reef, but most people will only ever get to see its wonders in photos.

“It’s challenging to get the weather window. It’s pretty rare to be able to dive out there,” Mr Testoni said.

“It’s one of the most challenging dives you can do in Tassie. It’s a pretty special place.”

What lies beneath

Mr Testoni said when descending at the Hippolytes, the first remarkable thing he noticed was that the bull kelp grew down to about 15 metres, a lot deeper than other sites.

“Once you get about 30 metres deep, a lot of the seaweed stops and you end up with these amazing coral and sponge reefs that are super colourful and super vibrant,” he said.

“People don’t realise there are these amazing colourful reefs down deep there, filled with fish.

“You see thousands of fish at a time, over 20 species.”

Some of the species include butterfly perch and large schools of real bastard trumpeter.

“You get lots of boarfish and I’ve seen a few big blue fin tuna swimming around down there,” Mr Testoni said.

“One of the hazards is that there are often tuna fishermen buzzing around above you when you’re out there.”

Mr Testoni went down to about 55 metres on his most recent dive at the site, and believes it gets down to about 65 metres.

Rocks claim ships

The Hippolyte Rocks dive site has several different areas, including the rocky islands known as ‘big Hippolyte and little Hippolyte’, which is 65 metres at the highest point.

A rock known as the Needle sits between the two Hippolytes, and the Pie is a rock just below the surface that turns into large canyons.

It was the Needle that claimed the ships Noord and Tasman.

Mr Testoni said the Tasman wreck was down at 70 metres, requiring specialised equipment to dive it.

The Tasman was a large cargo ship that had 27 crew and officers on board as well as 29 passengers when it hit the rocks in 1883 during a Hobart to Sydney voyage.

According to the Australasian Underwater Cultural Heritage Database, the captain was returning to his watch when he “rushed on deck and was shocked to find the vessel where she had no business to be, between the Greater and Lesser Hippolytes”.

The other wreck, the Nord, was wrecked in 1915 while carrying 12,000 cases of benzine to Hobart from Melbourne.

The database reports the Nord took the same path as the Tasman, seeking the calm water between the Hippolytes, which was described as an “unforgivable oversight”.

But the captain was cleared of blame for the wreck due to an inaccurate chart.

Mr Testoni has dived the Nord wreck site, which lies at about 40 metres.

“It’s all surrounded by sand and then in the middle of this sandy patch is two pieces of ship where it’s almost split in half,” he said.

“It’s covered in fish and there’s very often seals roaming about it and hunting on it.”

Experience required

Mr Testoni said it was possible to dive the area on a recreational licence down to 40 metres and there was plenty to see at that depth.

He said past 40 metres would require a technical diving licence.

“I would say if you’ve got at least 60 dives and a deep licence, that’s the level where you could go out with a professional operator and do a dive on it,” he said.

The weather conditions need to be perfect to dive the rocks, and he said the Easter long weekend was one of the few weekends in the past year that had made it accessible.

“It’s so exposed, you need no swell coming in and a wind coming from the west,” he said.

“It’s definitely not a dive for someone inexperienced.”