Tin Mine Cove is the loneliest site in this list – a small beach on the north-eastern tip of the Prom facing Corner Inlet, named for a short-lived tin mine of the 1920s whose relics lie in the scrub behind the beach, and reached only by the Prom's northern circuit walk or by boat across the inlet. It sits inside the Corner Inlet Marine National Park rather than the Wilsons Promontory one, and Scuba Doctor lists it at 2–15 m for Open Water divers, noting that the site slopes off gently from the beach to a depth of 15 m about 50 m offshore, that snorkellers should walk to the point from the beach and scuba divers should anchor a boat next to the big boulder at the north end of the beach. The dive is a granite point and boulder slope dropping into the inlet's seagrass and sand, and the interest is the meeting of two habitats: on the rock, kelp and algae with wrasse, leatherjackets, zebrafish, old wives, abalone and small crayfish (protected), sponges and ascidians on the shaded faces; on the sand and seagrass, the inlet's nursery fauna of King George whiting, flathead, stingarees, pipefish, seahorses, cuttlefish and juvenile fish, with rays and the occasional smooth stingray in the channel.

Corner Inlet's Posidonia seagrass meadows are the largest in Victoria and the park protects them; divers should keep off the beds. The deep channel just off the cove carries strong tidal currents and is the reason the dive is done at slack water and kept close to shore. Visibility is inlet-grade, a few metres to 10 m on a good neap.

Nobody dives Tin Mine Cove regularly – it is a site for overnight walkers with a mask, or for a boat exploring the northern Prom from Port Welshpool – but it is a genuine wilderness dive in a park most divers never see, and a reminder that the Prom's marine parks include the sheltered inlet as well as the Bass Strait islands.

Tin Mine Cove is reached on foot only via the Prom's northern circuit walk – roughly 20 km from the Five Mile Road car park via Barry Creek and Chinaman Long Beach, an overnight trip with a permit – or by boat across Corner Inlet from Port Welshpool (about 15 km, 30–40 minutes) or from the Yanakie/Duck Point ramps. Scuba is only practical by boat: anchor beside the big boulder at the north end of the beach and dive from there. The site slopes gently from the beach to 15 m about 50 m offshore.

Sheltered from ocean swell inside Corner Inlet but exposed to northerly and north-easterly wind chop across the inlet, and governed by tide: best dived at slack water, and Scuba Doctor warns against venturing far offshore because a deep channel just off the cove is subject to strong tidal currents. Visibility is Corner Inlet visibility – modest and best on the last of the flood on a neap. Summer and autumn; the walk-in track is closed or waterlogged in wet winters.

From a boat anchored by the big boulder at slack water, descend and follow the granite point and its boulders down the gentle slope to 10–15 m, staying inside the edge of the channel, then work back along the seagrass and sand towards the beach. Snorkellers work the point and boulders from the beach. Abort if current builds.

No operator. Shore dives and snorkels done by campers at Tidal River and by clubs (Dive La Trobe, VSAG, Melbourne University Underwater Club) on Prom camping trips; No air fills at Tidal River or Port Welshpool; the nearest compressor is roughly 100 km away (Melbourne's south-east or Inverloch/Leongatha area by arrangement) – bring all cylinders or a portable compressor