HMS J7 (later HMAS J7) was a operated by the Royal Navy and the Royal Australian Navy.
Design and construction
The J class was designed by the Royal Navy in response to reported German submarines with surface speeds over . The submarines had a displacement of 1,210 tons surfaced, but J7 had a lighter submerged displacement than her sister boats, at 1,760 tons. 44 personnel were aboard.
Operational history
After the war, the British Admiralty decided that the best way to protect the Pacific region was with a force of submarines and cruisers. Some years later a stone marina was constructed around the wreck, which was left in situ and visible, being too expensive to remove, where it continues to deteriorate.