The Vernon Islands – East, North West and South West Vernon, known to the Tiwi as the Potinga Islands – are low coral islands in Clarence Strait, north of Gunn Point and south-east of Melville Island. Each is surrounded by a coral reef that is exposed at low tide, and navigation lights guide shipping through Howard Channel between them. The islands have been a conservation reserve since 1979 and were returned to the Mantiyupwi Tiwi people in 2018.

For divers, the Vernons offer something unusual close to Darwin: reefs that rise steeply out of deep tidal channels. The Marine Life Network notes that Spanish mackerel often feed around the reefs, and the combination of steep edges and fast-moving, relatively clear water brings pelagics close in. The reef slopes carry hard corals – staghorn, vase, plate and massive forms – together with leather corals (Sarcophyton), sponges and gorgonians, while the reef flats support seagrass, algae and a rich invertebrate fauna.

Field-naturalist surveys on the reef flats have recorded turtles, blue-ringed octopus, mantis shrimps, ass's-ear abalone and many molluscs and crustaceans; underwater, expect coral trout, sweetlips, snapper, angelfish, parrotfish, batfish and fusiliers, with juvenile blacktip reef sharks and tawny nurse sharks in the shallows and Spanish mackerel, golden trevally and queenfish on the edges. Dugong feed on the seagrass.

The Vernons are an intertidal coral locality of real significance, and they are threatened by proposals for industrial port development at nearby Glyde Point. Diving them demands respect for the tide: the channels run fast and slack is short. They suit advanced divers who are comfortable with drift diving from a live boat, and they are one of the best natural reef options within a day's boating of Darwin.

The Vernon Islands lie in Clarence Strait between Gunn Point and Melville Island. The closest launch is the concrete ramp at Leaders Creek, which the Marine Life Network notes is quite close to the islands (drive via the Arnhem Highway and Point Stuart/Leaders Creek roads, roughly 2.5 hours from Darwin). Boats from Darwin's Buffalo Creek ramp at Lee Point or from Cullen Bay run east across Shoal Bay and past Gunn Point – a longer open-water trip.

The islands are ringed by reef flats that dry at low tide; approach on a rising tide with a careful lookout.

Clarence Strait funnels Darwin's big tides between the mainland and Melville Island, and the channels beside the Vernons run very hard. Dive only on neap tides and at slack water – typically less than an hour – or as a controlled drift with a live boat. Dry season (May–October) mornings are best before the south-east trade wind builds; wind against tide in the channels creates steep, dangerous chop.

The wet season brings monsoon winds, run-off, cyclones (November–April) and box jellyfish.

Drop on the reef edge upstream at the start of slack, descend to 10–15 m along the slope and drift gently with the reef on one shoulder. Watch for Spanish mackerel and trevally out in the blue. Put up an SMB before ascending; the boat follows the bubbles.

Abort if the current starts to accelerate.

No scheduled dive trips. Sea Darwin runs occasional eco reef-walk and snorkel trips to the Vernons; Darwin Sub Aqua Club members and private boats dive the reef edges on neap tides.