WHAT does a ship do when it is in danger of collapsing? It pulls out its big guns, of course.

At least that's what is happening to the HMVS Cerberus at Black Rock. The ship's four muzzle-loading guns, each weighing 18 tonnes, will be removed in a bid to prevent the wreck from further collapse.

Once Australia's most powerful warship, the Cerberus was scuttled at Half Moon Bay in 1926 to provide a breakwater and is protected under the Victorian Heritage Act.

A major collapse occurred during a storm in 1993, hastening the decline of the rusting hulk.

Victorian Heritage Council chairwoman Chris Gallagher said it was hoped removing the guns would prevent further collapse.

"The Cerberus is one of the most historically important naval vessels in existence and has world-wide significance in the history of naval architecture," Ms Gallagher said.

KV Johnson Constructions is doing the removal work, funded under the State Government's Victorian Heritage Program.

The guns will be left on the seabed to prevent further deterioration.