In 2011 NT Fisheries expanded the Lee Point reefs with 600 six-metre concrete culverts laid in square and diamond patterns forming a structure 3.6 km long between and around the Rick Mills and Bottle Washer reefs. The Lee Point reefs are NT Fisheries artificial reefs in about 15 m on the open coast north-east of Darwin, built up since the 1990s from decommissioned plant, concrete culverts, shipping containers and old vessels, and expanded in 2011 with 600 six-metre concrete culverts laid in a 3.6 km pattern between the Rick Mills and Bottle Washer reefs. Local fishers and DSAC have added small scuttled boats. The reefs are primarily fishing structures, so expect boats on the marks and fishing tackle on the bottom, but they give divers structure, fish and shelter from the harbour's tidal race.

For divers, the culvert field is less a single site than a connecting network: rows and clusters of large concrete pipes on the sand in about 15 m, each one a shelter for fish. Because the culverts are laid in lines, they are a useful navigation aid for a drift-style swim on a neap or for linking the bigger reefs, and they reduce pressure on the older structures by spreading fish and anglers over a wider area. Species are the same as on the neighbouring reefs - jewfish, snapper, cod, Spanish flag and mackerel - with rays and small reef fish on the sand between. There is little published about diving the culverts specifically, and they are mostly fished rather than dived, so treat any visit as exploratory. Easy depth and simple structure make them suitable for Open Water divers comfortable navigating by compass. The pattern layout is published by NT Fisheries; check it before the trip so you know which way the lines run from your drop point.

Boat only. The nearest launch is the Buffalo Creek boat ramp at Lee Point, at the end of Lee Point Road about 20 minutes' drive north of the CBD (trailer parking, but a tidal creek - check the tide for launching and retrieving). From there the reefs are a short run offshore; from Cullen Bay Marina allow roughly 30-45 minutes around East Point and along the Nightcliff-Casuarina coast.

NT Fisheries publishes GPS positions for each reef. The area is open to the north and north-west, so pick a calm dry-season morning and dive the neap high-water slack.

Tide is everything on the Darwin coast: the spring range is 7-8 m and tidal streams run hard through the harbour, so diving is generally only possible on neap tides (range under about 3-4 m), timed to the slack at high water when clearer ocean water sits over the site. Spring tides bring strong currents and silt-laden water with near-zero visibility. The dry season (May-October) gives the most consistent conditions; the Lee Point reefs are sheltered from the south-east trades by the land in the morning, but afternoon sea breezes and any north-westerly make the open coast rough.

In the wet season (November-April) run-off from the rivers and creeks drops visibility, afternoon storms build quickly, and the harbour is in cyclone season; box jellyfish are present October-May.

Drop a shot on a culvert cluster found on the sounder, follow the line of culverts in one direction on a compass heading, turn at half gas and retrace the line. The culvert rows make a natural navigation guide.

No regular dive charters; dived by Darwin Sub Aqua Club on neap-tide club days and by private boats. Local operators may run a trip on request.