It's the new black: sub takes a trip across the harbour for a clean-up

HMAS Onslow headed across the harbour to Garden Island for a major overhaul this morning, its first in four years.

In marked contrast to its stealthy past, the old Cold War warrior was towed to Thales at Garden Island Dockyard at 9am.

Onslow, owned by the Australian National Maritime Museum, was launched in 1968 and decommissioned from the Royal Australian Navy in 1999.

It will undergo a two-week refit that will include an extensive cleaning of the hull by high pressure blasting to remove four years' worth of marine growth, removal and treatment of rust, and repairs on the rear torpedo tubes.

Finally, the sub will receive a fresh coat of paint … in submarine black of course.

Onslow was one of six Oberon class submarines that formed the Australian Submarine Squadron in the Royal Australian Navy from the late 1960s.

Just 89.9 metres long and with a complement of 68 submariners, Oberons were considered to be the most advanced types of conventional submarine, combining high speed and great underwater endurance with anti-surface vessel and anti-submarine attack capabilities.

Thousands of visitors to the National Maritime Museum climb on board HMAS Onslow each year to experience the world of underwater warfare, exploring its torpedo hatches, cramped sleeping quarters and narrow work spaces.

The submarine is expected to return to the museum on June 1.