Australian-built 40-foot launch AMETHYST (AWB 420) was part of a post-WWII series of work boats built for the Australian Army and later acquired by the Royal Australian Navy. Workboats attached to Garden Island (Fleet Base East) pound were not named, but launches that served Spectacle Island depot in Sydney were named GARNET (444), ONYX (416), TOPAZ (404) and AMETHYST (420)*

*Source: The Register of Australian and New Zealand Ships and Boats http://www.boatregister.net/WW2_ArmyWorkBoats.html

In this image, AMETHYST (AWB 420) is viewed through the window of the old rigging room on Spectacle Island, with Snapper Island in the middle distance. In the foreground is the scaled replica model of 420 built by David Glasson with model of Stannard Brothers Tug TEMORA in the background.