HMVS Cerberus is a breastwork monitor, a type of turreted warship designed in the 1860s by Edward Reed. Launched in 1868 to defend the Australian colony of Victoria, Cerberus was named after the three-headed mythical dog which guarded the entrance to Hades. Following Federation, the ship was absorbed into the Commonwealth Naval Force, which later became the Royal Australian Navy (RAN). In 1921, the ship was renamed HMAS Platypus, and was tasked as a tender ship for the RAN's flotilla of six J class submarines. The ship was sold for scrap in 1924, then sold again in 1926 for use as a breakwater in Half Moon Bay, Black Rock, Victoria. Cerberus is one the few surviving examples of a monitor warship in the world, but is currently rapidly deteriorating; the remains of the ship are visible from the local beach or pier. A local campaign to save the vessel has thus far failed to raise the required capital. Cerberus had a sistership Magdala.