The Temple is the signature site of Moon Island, the flat rock off Swansea Heads at the mouth of Lake Macquarie. Grey Nurse Charters describes a massive sea cave in the south-eastern wall, to about 20 m, with a coral-encrusted rock formation - the altar - blocking half the entrance. Inside is a genuine dark zone, and iNaturalist observers describe it as a massive overhang cave with a large dark zone and a boulder-blocked entrance.

The Temple matters for one reason above all: critically endangered grey nurse sharks shelter in the cave, most reliably from late June until September and especially during the winter salmon runs. Seeing these big, ragged-toothed but placid sharks hanging motionless in the gloom beneath the altar is one of the best shark encounters in the Newcastle region. Outside shark season the cave remains impressive, and the site is surrounded by fish - pomfrets and bullseyes in the entrance, pike and kingfish along the wall, pelagics in the blue, and wobbegongs resting on ledges.

Nearby, the Horseshoe Cave is a shallower U-shaped overhang coated in soft coral, a good add-on for the second half of the dive. The Moon Island walls here are 10 m or deeper and pocked with caves of various sizes, so there is plenty of structure to explore. Eastern blue devilfish, weedy seadragons, bull rays and Port Jackson sharks are all recorded around the island, and turtles occasionally appear.

The dive suits Advanced divers or guided Open Water divers with good buoyancy and awareness of shark etiquette. It is dived regularly by Swansea charters and is the reason many visitors come to Swansea in winter.

Boats launch from the public ramps inside Swansea Channel, either at Black Neds Bay beside the Swansea Bridge or at the Swansea/Lake Macquarie ramps, about 25 km south of Newcastle via the Pacific Highway. Parking with trailer bays is available at Black Neds Bay. The run is east along the channel, across the Swansea bar (check the bar and tide first - cross on the flood where possible) and a short distance out to the site; Moon Island sits just off Swansea Heads (Reids Mistake), so the run from the bar is only a few minutes - total 10-15 minutes from the ramp.

The Temple is on the south-eastern side of the island; the boat anchors in sand off the wall or drops divers and follows their bubbles.

Moon Island and the reefs off Swansea Heads sit just outside the Swansea Channel bar, which is the deciding factor on most days: the bar is dangerous in any sizeable easterly or south-easterly swell and on a run-out tide, and Marine Rescue Lake Macquarie should be checked before crossing. Offshore, the sites prefer swell under about 1.5 m and light westerly or northerly winds; a strong nor'easter makes the eastern walls choppy, and a southerly swell pushes surge into the caves. Visibility runs 8-15 m and is best on a flooding tide, when clean ocean water replaces the lake outflow; after heavy rain the brown plume from Lake Macquarie can cover the inshore sites for days.

The Temple faces south-east, so a south-easterly swell produces surge in the cave mouth.

Descend to the wall and swim to the cave entrance, approaching from the side past the altar boulder. If grey nurse sharks are present, stay low and to the side of the entrance and do not enter or block their path. Continue along the wall to the shallower Horseshoe Cave overhang before returning to the boat.

Not a penetration dive - stay in the daylight zone of the cave mouth.

Grey Nurse Charters (Swansea) runs boat dives to the Moon Island and Swansea offshore sites most weekends and on demand; Dive Newcastle and local clubs also dive the area from private boats launched at Swansea.