Of the three services, the Navy's structure is the most flexible and indefinite. The Navy can be roughly divided into ships and shore establishments, a shore establishment being a naval base on land. Apart from the obvious material differences, however, there is little difference between the two. A naval shore establishment is commissioned just like a sea-going vessel and, just like a sea-going vessel, is known as Her (or His) Majesty's Australian Ship. Although they have different jobs to do, the personnel at a naval base are also organised in a similar manner to those aboard ships, having daymen, watchkeepers and duty watches.
A flotilla is composed of two or more ships: these can be destroyers, submarines, mine-sweepers, corvettes or light patrol craft. In the case of destroyers, a flotilla has a rigid structure. There are nine vessels in the flotilla, which are divided into two divisions of four, with another vessel leading. The divisions are further divided into two sub-divisions of two vessels. There is no fixed organisation for flotillas of the smaller vessels. In the case of three or more vessels, they can also be divided into divisions and sub-divisions. A flotilla is usually commanded by a captain, and a division by a commander. Destroyers and submarines are usually commanded by a lieutenant commander, and smaller vessels by lieutenants.