Bynoe Harbour is a large, mangrove-lined inlet between the Cox Peninsula and Dundee, south-west of Darwin. The Marine Life Network describes the reefs and islands adjacent to the harbour entrance as easily accessed from Dundee, and the area is well known to anglers, crabbers and pearl farmers. It is not a mainstream dive destination, but its reefs offer an alternative when Fog Bay is too rough.

Published detail is limited. Expect fringing reefs around the entrance islands and banks, with turbid-water coral communities – massive, encrusting and plate corals, leather and soft corals, sponges and gorgonians – interspersed with rubble, sand and seagrass. Big tides flush the harbour twice a day, so currents at the entrance are strong and visibility changes rapidly through the tidal cycle.

Fish life is rich: golden snapper, fingermark, black jewfish, estuary cod, coral trout and grunter on the reefs, with queenfish, trevally and mackerel at the entrance on the run of tide. Turtles and dugong use the seagrass, and rays are common on the sand.

SS Brisbane lies on Fish Reef north of Bynoe Harbour and Quail Island, and many divers visiting the area will be doing so as part of a Brisbane trip. Bynoe itself suits self-sufficient, experienced Top End divers who can read tides and accept poor visibility. Divers who explore here are encouraged to record positions, depths and conditions and share them with Darwin Sub Aqua Club, as very little about these reefs has been written down, and the harbour's pearl leases and crab-pot lines should be given a wide berth when anchoring.

Bynoe Harbour can be reached by launching at Dundee Beach and running north-east around the coast, or by launching inside the harbour at the Crab Claw Island ramp (off Bynoe Harbour Road, via the Cox Peninsula Road – roughly 1.5–2 hours from Darwin). Boats from Darwin can also come around the Cox Peninsula. Reefs are on the islands and banks at the harbour entrance; locate them on the chart and sounder and anchor in sand on the reef edge at slack water.

The Dundee coast faces west into the Timor Sea. The dry season (May–October) is the diving season: the south-east trade wind blows offshore, mornings are calm and water clarity is at its best. Dive on neap tides at slack water – tidal ranges here are large, currents run hard around reefs and headlands on springs, and beach launching and retrieval at Dundee also depend on the tide.

Afternoon westerly sea breezes can chop up the sea. In the wet season (December–April) monsoon north-westerlies blow straight onshore, rivers flood with run-off, cyclones are possible and box jellyfish are present, so diving is rarely feasible.

Dive only at slack water on a neap tide. Anchor on the reef edge, follow it at 5–10 m and stay close to the anchor line; abort if visibility is below 2 m or the current starts to run.

No dive operator based at Dundee. Private boats launched at Dundee Beach, occasional Darwin club trips, and fishing charters that may carry divers by arrangement.