Hop in a submarine, and take a ride down through the deep dark depths off Tasmania's south coast to discover an amazing underwater world. Massive mountains, canyons and hills rise hundreds to thousands of metres above the sea floor.

These sea mounts are the mountains of the underworld.

Look out the window to see weird and wonderful fish, crustaceans, corals and other animals, many of which have never been seen before.

Did you know that... ?


  • The sea mounts off the coast of Tasmania are remnants of extinct volcanoes.


  • Sea mounts range from 500 to 1000 metres in height. Some summits are more than a kilometre below the surface.


  • 9 out of 13 species of hydroids (a relative of coral) found by scientists have never been seen before.


  • Deep sea mount fish such as Orange Roughy (also known as deep sea perch) can live for more than 100 years.

What lives here?


On the seamounts:
Corals, soft seapens, sponges and seawhips attach themselves to the hard surfaces to form amazing underwater forests. Sea spiders crawl through these forests, while slipper lobsters make homes in burrows amongst the rock and coral. A wealth of worms and small crustaceans live in the soft sediment.


Around seamounts:
Orange Roughy and deepwater oreos swim continuously to avoid being swept away by strong currents. Deeper down, bizarre eel-like and blob-like fish can be found - the monsters of the deep.

Dr B. Diversity tells all

The most common species covering the Tasmanian sea mounts is a stony coral called Solenosimila variabilis.

Rugged terrain and strong water currents make sea mounts difficult to study, so there are many species yet to be classified by science. However, scientists do know that a lot of the fish and invertebrates are endemic (live only here and nowhere else).

Trapped nutrients from swirling water currents, plus small mobile animals like shrimps, are the major food source for deepwater fish. The currents also help remove waste products, keeping the ecosystem healthy.

Sea mounts are isolated habitats, so each sea mount has its own unique and diverse ecosystem.

Do whales drop in?

Whale species including blue, fin, sei, minke and humpback all swim over deep sea mountains on their yearly migrations to and from Antarctica. Only the sperm whale dives to the world of these undersea mountains in their hunt for giant squid.

Here in the year 2050?

Sea mounts are unique and sensitive habitats. Unfortunately, a great deal of damage has already been done. Scientists liken the damage to the destruction of rainforests on land.

Commercial trawl fishing is the biggest pressure. It causes:

  • Destruction of sea mount animals like corals, sea pens and sponges.
  • Over-fishing of sensitive fish stocks, such as Orange Roughy.

Once depleted, sea mount species require decades, if not centuries, to recover. In fact, on some sea mounts in other parts of the world, commercial fish species have been wiped out.

To make sure that the sea mounts stay around into the next century, they need to be protected in marine parks and reserves, and the threats affecting them need to be stopped.