HMS J5 (later HMAS J5) was a First World War J class submarine built for the Royal Navy by HM Dockyard at Devonport in Plymouth. The J's were three-screw diesel electric submarines of some 1,800 tons armed with six torpedo tubes, two of these in the beam position, and a 4-inch gun. They were built to have a fast surfaced speed; in practice nearly 20 knots. The wreck of the J5 lies in of water at and can be accessed by experienced divers.