Amphibalanus improvisus was detected on a vessel berthed in Hobart in 2014. The vessel was berthed for approximately 12 months prior to the detection of the barnacles. Once detected all barnacles were removed from the vessel and there was no indication of establishment of A. improvisus in the environment surrounding the vessel. In 2017, a small number of  A. improvisus were found on the hull of a boat in Hobart that had only recently arrived. Any specimens detected during a dive inspection of the vessel were removed.

Amphibalanus improvisus is a sessile crustacean that has a smooth, white conical shell. The shell can be up to 17 mm in diameter and 10 mm in height (Olenin, 2006). The opening of the shell is diamond-shaped and toothed and the base of the shell is radially calcereous, flat and thin and permeated with pores (Zaiko, 2005).