HMAS Waterhen

HMAS Waterhen is a Royal Australian Navy base at Waverton, on the lower north shore of Sydney Harbour, New South Wales, Australia. It is the RAN's mine warfare and clearance diving base and forms part of Fleet Base East. The Department of Defence owns the site; the base is commissioned as a stone frigate under RAN operation.

Waterhen hosts the Australian Navy Mine Warfare and Clearance Diving Group. Assigned elements include Clearance Diving Team One and the Huon-class minehunters HMAS Diamantina and HMAS Yarra, together with minor war vessels and commercially operated support craft: the diving tender Seal, the navigation training vessel Seahorse Mercator and the multi-role aircraft training vessel MV Sycamore. Since 2014 the base has also supported the LCM-1E landing craft embarked in the Canberra-class landing helicopter docks, numbered L4401 to L4412, with the LHD Landing Craft School conducting crew training at the site. Waterhen further serves as a berth for minor war vessels visiting or operating temporarily from Sydney.

Maintenance for the landing craft and the associated training programme are housed at the base. The site occupies a near-water-level plateau below a sandstone cliff face on Balls Head Bay, with wharves and shore buildings dating from the reconstruction of the mid-1990s. Between December 1994 and December 1996 the entire base was levelled and rebuilt with new buildings, wharves and facilities at a cost of A$70 million.

The area came under military control on 15 March 1943, initially under joint Royal Australian Navy–United States Navy administration, and was used to store spare netting for the Sydney Harbour anti-submarine boom. It reverted to a storage site after 1945 before being selected in the early 1960s as the base for the RAN's minesweeping forces, then comprising six ex-Royal Navy Ton-class minesweepers and a clearance diving team. Commissioned as HMAS Waterhen on 5 December 1962, it was the first small-ship base established by the RAN; from March 1969 to 1979 its commander also held the appointment of Commander Australian Mine Warfare and Patrol Boat Forces, the patrol boat element passing to HMAS Cairns in 1979.