Pipeline Reef is one of the older, purely structural reefs in the Fenton Patches field. According to the NT Government artificial reef list it consists of about 200 tonnes of large concrete pipes dumped on the sea floor in around 25 m of water. It was built primarily as fish habitat for anglers, and it is dived far less often than the wrecks nearby, but it has a character of its own.

The pipes lie in a jumbled pile rather than a neat grid, creating a maze of tunnels, overhangs and gaps. Large-diameter pipes form short swim-through-sized tubes, but they are open to silt and fishing snags and are best looked into rather than entered. Their curved surfaces have become coated with sponges, hydroids, soft corals and oysters, and the shaded interiors are exactly the kind of habitat that big resident fish favour. Estuary cod and black jewfish commonly sit in the pipe mouths, golden snapper and saddletail snapper hover over the pile, and schools of baitfish attract passing trevally and mackerel. Look along the sand edges for stingrays, shovelnose rays and flathead.

The site is compact and uniform, so a single dive covers it; the interest is in the fish rather than the structure. Visibility over the pile can be poorer than on the taller wrecks because fine sediment settles between the pipes and is easily stirred by fins.

Pipeline Reef is a good choice as a second dive on a Fenton day when the wrecks are crowded with boats or when a diver wants a quieter site. It also works for photographers after big cod portraits. Depth and slack-water timing make it an advanced-level dive despite the simple layout, and good buoyancy control is needed to stay off the silt.

Fenton Patches lies about 17 nautical miles (roughly 31 km) north-west of Darwin in open water beyond the harbour mouth, so it is a boat-only site. Club and charter boats usually launch from the Cullen Bay ramp and marina (Marina Boulevard, Larrakeyah – ample trailer parking) or from Dinah Beach / Sadgroves Creek ramps inside the harbour, then run out past East Point and across Beagle Gulf. In a fast 6–7 m trailer boat allow roughly an hour each way in trade-wind chop; slower in a southeasterly above 15 knots.

There are no public moorings: the site is found on GPS and sounder, and a shot line or grapnel is dropped on the structure. Private boats need a competent skipper who can work the tide and keep a boat cover on the surface while divers are down.

Fenton Patches is open water in Beagle Gulf with no shelter. Dive it only on neap tides and time the dive for slack water (typically a window of 30–60 minutes around the turn; Darwin's tidal range reaches 7–8 m on springs and currents at Fenton run hard outside slack). The dry season (May–October) brings the south-east trades: mornings are usually calm, but a 15–20 knot south-easterly by late morning makes the run back uncomfortable, so plan an early start.

The build-up (October–December) brings glassy days but storms in the afternoon; the wet season (December–April) brings north-westerly monsoon winds, heavy run-off that cuts visibility, cyclone risk (November–April) and box jellyfish in the water. Visibility is best after several days of neaps and no rain.

Drop the shot onto the pipe pile and descend together. Explore the pile in a slow clockwise circuit at 22–25 m, looking into the pipe mouths for cod and jewfish and checking the sand margins for rays. Do not enter pipes.

Keep the shot in sight in poor visibility or run a reel. Ascend the shot line for the safety stop before the tide turns.

No daily operator. Darwin Sub Aqua Club (DSAC) runs member boat dives to Fenton Patches on suitable neap-tide weekends in the dry season; Dive Darwin (learntodivedarwin.com.au) and Western Blue Dive Charters offer outer-harbour/offshore wreck trips on demand when tides and weather line up. Otherwise private boat only.