The Sanyo Maru was a Japanese pearling mother-ship of about 36 m that supported a fleet of pearling luggers working the Arnhem Land coast in the 1930s, when Japanese crews dominated northern Australia's pearl-shell industry. On 1 July 1937 she sank in a sudden squall, reportedly dangerously overloaded; two people died. Much of her cargo was salvaged in the late 1930s and her location was then forgotten.

The wreck was rediscovered around 2012 – historical records and Aboriginal researchers provided a key clue, and the Navy located the site – and it was subsequently investigated by maritime archaeologists with support from Paspaley, Bhagwan Marine and the Western Australian Museum. She lies in about 26 m. Around 70 artefacts were recovered, including ceramic bowls, bottles, lacquerware, surgical kits, personal items, diving equipment and a shell-encrusted glass lantern, and these formed an exhibition at the Australian National Maritime Museum in 2022.

In 2013 the Australian Government declared a 200 ha protected zone around the wreck under the Historic Shipwrecks Act, and it is one of three NT closed-water protected zones alongside Florence D and I-124. Entry requires permission from the NT Heritage Branch.

The Sanyo Maru is historically important as one of the few physical remains of the Japanese pearling era off Arnhem Land and its links with Yolŋu communities. It is not a recreational dive site; it is listed here so divers know it exists and that it is closed. The best way to see the site is through the museum collection and published archaeological reports, which document the daily life of the Japanese crews and the pearling economy that once linked Broome, Darwin, Thursday Island and Arnhem Land.

The wreck lies off the central Arnhem Land coast, about 300 miles north-east of Darwin and some 60 km from Maningrida. The surrounding 200 ha protected zone is closed water – entry requires NT Heritage Branch permission – and the adjacent coast is Aboriginal land requiring Northern Land Council permits. There is no recreational access; archaeological teams reach it on expedition vessels.

Open Arafura Sea off Arnhem Land. Archaeological work has been done in the dry season on calm, neap-tide days. The site is closed to recreational divers; The central Arnhem Land coast is affected by the Liverpool and Blyth river outflows, so visibility is best late in the dry season.

South-east trades blow strongly from May to September and can make the Arafura Sea rough by midday; the wet-season monsoon, cyclones (November–April) and box jellyfish apply to any visit.

Not applicable – closed site.

None – closed-water protected zone; archaeological expeditions only.