Cabbage Tree Island is a nature reserve island off Port Stephens whose shallow rock walls have made it a favoured training and intermediate-level dive site, offering a genuinely safer, more approachable profile than the more exposed and current-affected Broughton Island group further offshore. Depths here range widely, from a comfortable twelve metres on the shallower shelves out to a genuine forty metres on the deeper faces, giving operators flexibility to run anything from a relaxed open-water dive to a more demanding deep excursion depending on the group and conditions on the day. The island's closer position to Nelson Bay — a run of around twenty minutes rather than the fifty-plus needed to reach Broughton Island — also makes it a practical choice when time, weather or group experience level rules out the longer offshore trip.

As with the broader Port Stephens islands group, Cabbage Tree Island sits within the network of protected areas supporting the region's grey nurse shark population, and while it is not one of the named critical habitat aggregation sites in the way Broughton Island's Looking Glass or Shark Gutters are, sightings are a real possibility given the general movement of sharks between sites along this stretch of coast. The island's general reef life follows the typical Port Stephens pattern of temperate species mixed with occasional subtropical visitors, and its main appeal for local operators is precisely its safety and flexibility — a reliable, moderate-risk option that works for a broader range of diver experience levels than the more committing sites further offshore, making it a frequent choice for training dives, refresher courses and groups with mixed experience levels.

Boats depart Nelson Bay marina and run out past the harbour heads to the islands scattered along the Port Stephens coast — Cabbage Tree Island, Boondelbah Island, Little Island and Fingal Island are all within roughly 15-30 minutes of Nelson Bay, considerably closer than the longer run out to Broughton Island. Exact site choice on the day depends on wind and swell direction, since the different islands and their different sides offer shelter from different conditions.

The Port Stephens islands sit on the open coast just outside the harbour and are exposed to ocean swell, though generally less so than Broughton Island given their closer, more sheltered position relative to Tomaree Head and the harbour entrance. Operators choose the specific island and side to dive based on the day's wind and swell direction. Visibility is typically 8-20 m and best in settled autumn/winter weather; it drops after rain and in a strong onshore blow.

Descend onto the shallow rock wall around the island and work along its base, extending to deeper sections (25-40 m) for more experienced divers, watching for typical Port Stephens island reef fish and the possibility of grey nurse sharks given the island's proximity to the area's critical habitat network.

Let's Go Adventures (Nelson Bay) and Feet First Dive (Nelson Bay) both run regular boat trips to the Port Stephens islands group, weather permitting.