Connexion Island (often spelled Connection Island) lies off Alyangula, the mining township on the west coast of Groote Eylandt, and is named by the Marine Life Network as one of the island's best dives, alongside Zodiac Rock and the dolphins at the wharf. Groote Eylandt is the largest island in the Gulf of Carpentaria and the home of the Anindilyakwa people, and diving there is almost entirely a pursuit of the resident community.

The Marine Life Network notes that as you move into the Gulf, the big tides and river outflows of the western Top End lessen, visibility improves and coral reef life becomes more prolific in shallower depths, with dives spanning roughly 2–30 m and more. Around Connexion Island this means fringing reefs with hard corals – plates, branching staghorn and massive forms – soft corals and sponges, and a busy community of reef fish: damselfish, anemonefish, butterflyfish, angelfish, parrotfish, wrasse, coral trout and sweetlips. Turtles are common in Groote waters, dugong graze on seagrass nearby, and trevally and mackerel pass along the reef edge.

Its advantages are proximity to Alyangula, shelter from the south-east trade winds on the west coast, and the clearer Gulf water.

The main obstacles are logistical rather than underwater: a land-council permit, limited accommodation, and the need to bring or arrange your own gear, air and boat. It suits self-sufficient Open Water divers with local contacts, and it is a good first dive for anyone who finds themselves on Groote Eylandt with a free morning and a boat.

Groote Eylandt is about 630 km east of Darwin: fly to Groote Eylandt airport (about 1.5 hours from Darwin or 40 minutes from Nhulunbuy). A recreation permit from the Anindilyakwa Land Council is required before visiting, and commercial accommodation is limited – the Aboriginal-owned Dugong Beach Resort is the main option, as the mining company does not provide tourist accommodation. Boats launch at Alyangula on the island's west coast; sites are a short run from town.

Accessing dive gear on the island may be difficult – bring your own and arrange fills in advance.

Groote sits well inside the Gulf of Carpentaria, where tidal ranges are much smaller than at Darwin and there is less river outflow, so visibility and coral life are better in shallow water. From April to September the south-east trade wind blows strongly and the west-coast sites around Alyangula are in its lee, making them diveable on most mornings. The build-up (October–December) brings the calmest seas.

In the wet season (December–March) the monsoon can bring north-westerly winds onto the west coast, cyclones form in the Gulf, and box jellyfish are present; inshore visibility drops after heavy rain.

Anchor in sand off the island's fringing reef on the lee side. Follow the reef slope at 8–15 m with the reef on one shoulder, turn at one-third gas and return shallower through the coral gardens at 3–6 m for a long safety stop.

No commercial dive operator on Groote Eylandt. Diving is done by residents (mostly mining-community members) with private boats; Dugong Beach Resort and Groote Eylandt Sports Fishing run fishing trips and may assist by arrangement. Visitors must bring or arrange their own dive gear and air.