Gem - Rottnest Island snorkelling

The Gem was a 52-ton wooden cutter, built as a yacht at Cowes in 1835, that sank off Thomson Bay on the morning of 18 May 1876 while carrying 500 bags of wheat from Port Irwin to Fremantle. She was seen early that morning running for the anchorage with all sail set and no sign of trouble. When the Fremantle light-keeper looked again, only her topmast and crosstrees showed above the water.

All ten people aboard - six crew and four passengers - were lost. Macassan divers found only a rug in the captain's cabin, and the ship's boat was still tied to the stern with signs that someone had tried to cut it free. Over the following days decking, belongings and sacks of grain washed ashore. A sudden leak that swelled the wheat, a strike on Kingston Reef and even a cover-up by the harbour master have all been suggested, but the cause has never been settled.

The wreck lies on sand in about 10 metres of water, some 300 metres south-east of Kingston Reef inside the Kingston Sanctuary Zone, and is reached by boat. Little remains beyond the keel, ribs and some planking, often under weed.

• Experience level: Advanced
• Depth: 8-10 m
• Access: Boat needed: about 1.3 km off Thomson Bay near Kingston Reef. At 8-10 m and mostly covered in weed, the wreck is effectively a scuba dive; little can be seen from the surface. Inside the Kingston Reef sanctuary zone; protected wreck.
• Historic Wreck (1876)
• Unsolved Mystery
• Wooden Cutter
• All Hands Lost
• Wheat Cargo
• Kingston Sanctuary Zone

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