Pelsaert Island is the long, narrow southern island of the Abrolhos, named for the Batavia's commander. Marine Life Network describes two related sites on its east side. The Pelsaert Island reef, 6-25 m, has varied topography, WA dhufish, baldchin groper and butterfly cod (lionfish), with visibility often exceeding 20 m. The Pelsaert Drop-off, 5-25 m and dived as a drift, is a fish sanctuary for experienced divers, with rock lobsters, moray eels, wrasse, parrotfish, lionfish and gropers.

The combination of clear water, a sanctuary and tidal flow along the wall makes this one of the best dives in the southern group.

The Pelsaert Group is the furthest group from Geraldton and the least visited, so liveaboards usually schedule it on the calmest days of a trip. Pelsaert Island itself is a low, narrow strip of coral rubble and sand that gives only partial shelter, and the island is an important seabird nesting site with restricted landing. Dive the drop-off with the tide, keep buddies close, and carry a DSMB and whistle for pickup.

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. Pelsaert Island is in the southern Pelsaert Group, about 60-70 km from Geraldton.

The drop-off is on the east side and is usually dived as a drift from a tender.

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. The east side of Pelsaert Island is sheltered from south-westerly swell but carries tidal current; Marine Life Network rates the drop-off for experienced divers.

Drop in at the top of the drop-off, drift along the wall at 15-20 m with the current, look into ledges for crays and morays, and ascend on a DSMB.

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.