The Shark is Rottnest's other WA Museum-recommended snorkel wreck and one of the most photographed. She was a steel hopper barge (a dredge spoil barge) that broke free from her moorings at Fremantle and drifted across to Rottnest, grounding on Henrietta Rocks in 1939 (1938 in some sources). She has remained there ever since, and parts of the hull still break the surface, making her easy to find.

The wreck sits in about 2-4 m on a mix of reef and sand just off the beach below Lookout Hill. The broken plates and frames have become an artificial reef colonised by weed and small invertebrates, with wrasse, juvenile bream, sweep and small reef fish sheltering inside. The surrounding limestone reef and seagrass add to the interest, and SeaLink describes the site as an 'underwater playground' for snorkellers.

This is a snorkel for calm days rather than a scuba destination: it is very shallow, visibility is moderate and surge quickly makes the jagged metal dangerous. The Museum recommends a shirt or wetsuit top and even garden gloves for protection. It suits families, confident beginner snorkellers and cyclists doing the island loop, and it is often combined with Parker Point and Little Salmon Bay further along the south coast. Protected under heritage legislation; do not climb on or remove anything. Scuba adds little except longer time in the water, and gear has to be carried on a bike or bus, so most divers snorkel it. Arrive early in summer, when the beach fills by late morning, and check the wind the night before: a south-easterly change can make the site unusable within an hour. Rottnest Island Authority lists it first among its six best snorkel spots.

From Thomson Bay settlement cycle about 3 km south (roughly 10 minutes) on the main road towards Porpoise Bay, or take the Island Explorer bus to Stop 3 (Henrietta Rocks). Leave bikes at the car-park/bike rack above the beach and walk down the short path to the sand. The barge is plainly visible just off the beach on the rocks; snorkel out from the sand, approaching from the sheltered side.

Scuba divers must carry cylinders from the ferry - there are no fills on the island.

Henrietta Rocks face south-east and are only calm in north-easterly and easterly winds (SeaLink lists NE and E as the suitable winds); southerly and south-westerly winds and swell send surge through the wreck and make it unsafe. Divingwawrecks gives a limit of under 1 m of swell. Summer mornings before the sea breeze are best; visibility is often limited (2-8 m) by sand and surge.

Snorkel from the beach to the inshore end of the barge, circle it slowly keeping clear of the jagged plates, then explore the surrounding reef and sand; in flat conditions scuba divers can make a gentle 3-4 m circuit. Snorkellers should stay within easy reach of the exit point and swim with a buddy; scuba divers at these depths need no safety stop but should ascend slowly and surface near the float.

No operator required; self-guided snorkel promoted by the Rottnest Island Authority as a top snorkel spot; guided snorkel tours (Rottnest Snorkel) sometimes visit.