North Point Hole is a small, little-documented neighbour of North Point Reef. Marinelife.org.au describes it simply as a cavern in the reef extending down to the seabed at 26 m and 'full of marine life', with depths of 18-26 m. It lies only a short distance from the North Point ravine, so boats that have found one can find the other.

As with other Rottnest caverns, the interest comes from the limestone itself - an opening that drops through the reef to the sand - and from the fish that pack into the shade: bullseyes, old wives and sweep in the darker parts, buffalo bream and wrasse around the entrance, and western rock lobster and cuttlefish in the cracks. The depth brings in larger fish such as dhufish and samson fish at times.

Because published information is thin, divers should treat it as an exploratory dive and go with someone who knows it, or use it as an extension of a North Point Reef dive on a calm day. It suits Advanced divers with nitrox and good buoyancy. Note that marinelife.org.au lists the same coordinates for Cigar Reef, so check positions with a sounder before committing.

On a flat day with 20 m or more of visibility, looking up from the bottom of the hole toward the surface is a striking view, and the combination with North Point Reef makes for a well-rounded deep dive. Keep the group small inside the cavern and carry a torch to see into the darker recesses.

As for North Point Reef: charter or private boat from Fremantle, Woodman Point or Hillarys along the north coast (about 25 km, 60-70 minutes). Locate by GPS and sounder and anchor clear of the reef. 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.

Exposed to westerly and north-westerly swell; like North Point Reef it needs calm seas (under about 1.5 m swell) and light winds, typically summer and autumn mornings. 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 onto the reef at 18 m, find the cavern opening and follow it down to its floor at 26 m, then return to the reef top and make a slow ascent. 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. 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.