Long Island in the Wallabi Group is where the Batavia mutineers were tried and most were hanged in October 1629 – it is sometimes called Gallows Island. Underwater, Marine Life Network highlights it as an example of the Abrolhos overlap zone: tropical staghorn corals alongside temperate fish such as buffalo bream and baldchin groper, reached from a public mooring.

The shallow reef suits snorkellers and relaxed dives, and the historical association makes it a meaningful stop on a Batavia-themed itinerary that also includes the Batavia wreck site, Beacon Island and the West Wallabi forts. Little further dive detail has been published.

The Houtman Abrolhos lie 60-80 km west of Geraldton (about 420 km north of Perth). There is no public accommodation or camping on the islands, so divers visit on liveaboard trips departing Geraldton (a 3-5 hour crossing), on private vessels using the public moorings, or – for snorkelling only – on scenic-flight day tours that land on East Wallabi Island. Long Island is near Beacon Island in the Wallabi Group; a public mooring is available.

The Abrolhos sit on the edge of the continental shelf in the path of the warm Leeuwin Current, which keeps water at 20-24°C and supports the world's southernmost major coral reefs. The islands are exposed to the south-west swell and to strong southerly winds that blow most afternoons from October to March; the crossing from Geraldton is often rough. Marine Life Network recommends March-May and September-November; late summer-autumn highs give the calmest seas.

Western rock lobster season (15 March-30 June) brings fishing camps and boat traffic. Choose the lee side according to wind; the public mooring area is reasonably sheltered.

Descend from the public mooring, explore the staghorn thickets and reef edge at 5-12 m, and return to the mooring line.

Liveaboard only for diving: Image Dive – 'Southern Image', the only dedicated dive boat at the Abrolhos (4 days/4 nights from Geraldton, max 8 divers, 3-4 dives a day); Eco Abrolhos Cruises – 5-day small-group cruises from Geraldton with snorkelling and diving; occasional Perth club charters. Batavia Coast Dive & Watersports (Geraldton) runs Abrolhos trips when boats are available.