Blacksmiths Shallows is an easy, fun reef off Blacksmiths, the beach suburb immediately north of Swansea Channel. Grey Nurse Charters describes a large reef in about 7 m whose southern end has a swim-through arch, a tunnel and crevices, with schools of yellow-tailed scad and diverse reef fish, and notes it is sheltered from southerly swells. In short, it is a fun dive.

The southern end is where most of the interest lies. The arch and tunnel are short swim-throughs formed by the sandstone reef, and the crevices around them shelter bullseyes, pomfrets, moray eels and crustaceans. Because the site is shallow, light is good and colours are bright, and the swim-throughs are easy to photograph with natural light.

The rest of the reef is a mix of kelp, low ledges and boulders typical of the Newcastle coast. Yellowtail scad school over it in large numbers, with silver sweep, mado and luderick among them, while red morwong, blue groper, wrasse and leatherjackets feed on the reef. Wobbegongs and Port Jackson sharks rest on the sand edges, and octopus and cuttlefish are common.

At only 7 m, Blacksmiths Shallows gives long bottom times and suits Open Water divers, students and snorkellers from a boat on calm days. It is especially useful as a southerly-day alternative when Moon Island's walls are rough, and as a gentle second dive after the deeper Bonnie Dundee or the Newcastle offshore artificial reef. Snorkellers on the boat can also enjoy the southern end on flat days, when the arch is visible from the surface.

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; turn north after the bar to the reef off Blacksmiths Beach, only a few minutes from the channel entrance.

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.

Blacksmiths Shallows is sheltered from southerly swell, making it a good choice when a southerly rules out Moon Island's exposed walls; north-easterly swell makes it surgy.

Anchor near the southern end, explore the arch, tunnel and crevices first while air is fresh, then meander north across the reef, watching the yellowtail scad schools. Return to the anchor for a short safety stop.

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.