Big Ben is one of Newcastle's best-known offshore reef dives, a substantial rocky reef system off Nobbys Head that drops through a series of walls, caves and swim-throughs to a maximum of about 24 m. Unlike the shallower shore sites closer to the beaches, Big Ben has real vertical relief, giving divers genuine wall diving with overhangs and small cave-like recesses to explore rather than the low, rambling ledges typical of the shallower reefs. Scattered among the reef structure are the remains of old maritime wreckage — timber and iron fragments from vessels lost off this historically hazardous stretch of coast — adding an element of history to what is primarily valued as a scenic and fish-rich reef dive.The site's drawcard is its combination of topography and pelagic action: giant bull rays are a signature sighting, often found resting in sandy pockets at the base of the walls or cruising along the reef edge, while blue wrasse and other reef fish work the shallower sections and open-water pelagics pass over the top in warmer months.

Conditions are best at high tide during periods of low rainfall, when the Hunter River's freshwater and sediment influence on the harbour mouth is at its lowest and visibility opens up. Because the site sits in open water off a busy port entrance, current and boat traffic both need respect, and a shot line or drift plan is standard practice. Big Ben is regularly worked into Dive Newcastle's charter schedule alongside North Reef and The Limestones, making a short boat run from the harbour enough to string together two or three quality reef dives in a morning.

Charter boats and private vessels launch from Newcastle Harbour (Nobbys boat ramp or the marina) and run a short distance offshore to the reef, off Nobbys Head. Contact Dive Newcastle or a local charter for a scheduled trip, as this is not a shore-accessible site.

These are ocean shore dives fully exposed to Pacific swell, so a flat or near-flat sea and low easterly swell are essential — anything over about 1 m makes entry and exit across the rock platforms hazardous. Best conditions come after several calm days with a light westerly or northerly breeze; a building south-easterly or nor'easter blows the sites out quickly. The East Australian Current periodically pushes warm, clearer tropical-influenced water down this coast in late summer and autumn, lifting both visibility and the variety of fish life; a southerly current reversal brings cooler, greener water.

Visibility drops for several days after heavy rain due to river and stormwater runoff from the Hunter River and city catchments.

Descend the shot line to the reef top around 12 m, work down the walls and through the swim-throughs and small caves toward 24 m, checking ledges for bull rays and pelagics, then ascend back along the same wall to the shot for a safety stop.

Dive Newcastle runs regular boat charters to Big Ben as one of its signature offshore reef dives; other Newcastle-based charters and private boats dive it on suitable days.