The Pipeline is Port Stephens' dedicated muck-diving site, built not around any natural reef but around a 250-metre disused pipeline structure lying on the sand near the Nelson Bay marina and fish co-op, its concrete blocks and ballast creating the only significant relief on an otherwise featureless sandy bottom. Visibility here rarely exceeds five to eight metres and is often less, a direct result of the fine silt that blankets the area and lifts easily with any disturbance — but this is exactly the kind of low-visibility, structure-poor habitat that produces exceptional muck-diving results, and local guides rate it, without much argument, as the best macro dive site in NSW. The species list justifies the claim: seahorses and pipefish including rare varieties are found regularly along the structure, decorator crabs, cuttlefish and moray eels use the pipeline's nooks for shelter, rock lobsters shelter beneath the ballast, and blue-ringed octopus — stunning to see but genuinely dangerous if handled — are an occasional but real find for divers who know where and how to look without disturbing anything.

Because the visibility offers so little natural navigation cues, divers typically follow the pipeline itself northward or use a fixed compass bearing to relocate it after any detour, and a slow, deliberate pace pays off far more than covering distance. This is not a dive for scenery or big animals, and newcomers expecting a typical reef dive may be underwhelmed by the murk and the featureless surroundings — but for photographers and divers who love the search-and-find discipline of muck diving, the Pipeline delivers consistently and is one of the most specialised, rewarding sites in the whole Port Stephens area.

Park near the Nelson Bay marina/fish co-op area and follow the dirt track down to the water's edge. The pipeline structure itself lies on the sand a short swim from shore; follow it northward, or use a compass bearing of roughly 330 degrees to relocate it if visibility is poor, since the low-relief sand surroundings offer little else to navigate by.

Sheltered inside Port Stephens with minimal swell exposure, but visibility here is characteristically poor by Port Stephens standards — averaging around five metres — a product of the fine, silty sand bottom that any careless fin stroke will stir into a persistent cloud. This is a site where poor visibility is normal rather than a sign of bad conditions, and it does not noticeably improve with tide or season the way the harbour's rockier sites do.

Enter from the dirt track and swim out to the pipeline structure, following it northward along its 250 m length or navigating on a 330-degree bearing if the structure is lost in low visibility, moving slowly and using a torch to pick out the site's exceptional array of small, cryptic species hiding among the concrete blocks and ballast.

Feet First Dive (Nelson Bay) runs dedicated macro/muck-diving trips here; independently diveable by experienced divers comfortable navigating in low visibility.