Jackson's Rock is an isolated reef off the east end of Rottnest listed by marinelife.org.au as a 16-18 m site with ledges, gullies and caves that is 'packed with marine life'. Isolated reefs like this, surrounded by sand, act as oases, drawing in fish from the surrounding seabed, and this one is closer to Fremantle than most Rottnest sites, making it a useful option for small boats or a quick morning dive.

Expect the typical Perth offshore reef community: buffalo bream, western king wrasse, bullseyes and old wives in the caves, western blue groper, leatherjackets and morwong, sponges and small invertebrates on the walls, and the possibility of pink snapper and dhufish nearby. Western rock lobster may be found in the ledges; this reef is outside the Rottnest sanctuary zones, so fishing rules apply rather than sanctuary protections.

Published detail is limited to the short marinelife.org.au listing, so treat the site as exploratory. It suits Open Water divers comfortable at 16-18 m with a buddy who can navigate a small reef and find the anchor again. Because it lies in open water on the approaches to Rottnest, boat traffic can be heavy on summer weekends and a flag and DSMB are essential.

The reef makes a good alternative when the charter sites at Rottnest are crowded, and a sensible short trip for divers testing a new boat or practising navigation on a compact site. Take a compass bearing from the anchor at the start of the dive so you can find it again at the end.

From Fremantle or Woodman Point run west toward the east end of Rottnest (about 15-17 km, 30-40 minutes). Locate the reef by GPS and sounder; anchor on sand beside it. Rottnest lies about 18 km west of Fremantle; allow 45-90 minutes each way by charter or trailer boat depending on the site.

Follow Rottnest Island Authority mooring and anchoring rules - do not anchor on reef or in sanctuary zones - carry a marine radio and log a trip plan, as the crossing of Gage Roads can turn rough when the afternoon sea breeze arrives.

In open water between Rottnest and the mainland; exposed to wind chop from any direction and to south-westerly swell through the South Passage. Best on calm mornings before the sea breeze. General pattern at Rottnest: summer brings calm morning easterlies followed by a strong south-westerly sea breeze from late morning, so dive early; winter brings north-westerly fronts and large swell, with clear, calm spells between them.

Check the Bureau of Meteorology coastal forecast for swell height and period before committing.

Descend on the reef, circuit its ledges and gullies at 16-18 m, look into the caves, and ascend up the anchor line. Agree a turn pressure before descending (half gas, or a third where current is likely), carry a DSMB, and make a 3-minute safety stop at 5 m.

No regular operator - private boats and dive clubs (e.g. UWA Underwater Club) only. Nearest dive services: Perth Scuba, Bucket List Diver and Dolphin Scuba (Perth/Fremantle) run Rottnest boat trips; there are no dive shops or air fills on the island.