The Halcyon class was a class of 21 oil-fired minesweepers built for the British Royal Navy between 1933 and 1939. They were given traditional small ship names used historically by the Royal Navy and served during World War II.

The Grimsby class were a class of 13 sloops laid down between 1933 and 1940. Of these, eight were built in the United Kingdom for the Royal Navy, four in Australia for the Royal Australian Navy and one for the Royal Indian Navy. Main armament was initially two 4.7-inch (120 mm) guns for RN ships and three 4-inch (100 mm) for Australian ships, but armament varied considerably between ships, and was increased later.