Larkin Cove is the middle of the three small quartz-sand coves between Refuge Cove and Waterloo Bay, an 80 m beach of coarse white sand with seagrass in the deeper water and granite on its flanks. Scuba Doctor lists it at 2–25 m and identifies the primary attraction precisely: low granite swim-throughs and caves at 7 metres depth, the principal one 12 m long. The boulders here have settled to form a series of tunnels and roofed gutters just below the kelp line, big enough for a diver to pass through comfortably but low enough that fins disturb the weed and silt on the floor – the listing warns that silt is readily stirred up during exploration, so buoyancy and fin technique matter more than on the open walls elsewhere.

Inside and around the swim-throughs the rock carries sponge, ascidian and bryozoan patches with bullseyes, blue devils and the occasional bearded cod or conger in the dark; outside, the reef is typical eastern Prom kelp and boulder with wrasse, morwong, leatherjackets, old wives, cuttlefish and draughtboard sharks, and the seagrass off the beach has stingarees, flathead and pipefish. Beyond the cove the granite continues down to 25 m. Larkin Cove is a boat site – the overland trek from the walking track is too long for scuba – and is almost always dived as part of a Port Welshpool trip with Brown Head Pinnacle 500 m to the north-east and Bare Back Cove 1 km south, the three together making a full day on this stretch of coast.

It suits Advanced divers who enjoy shallow overhead-free swim-throughs and macro subjects, and it is a good sheltered option when the pinnacle is too current-affected.

Boat only. Launch at Port Welshpool (sealed all-tide ramp, jetty and trailer parking on Corner Inlet, 2.5 hours from Melbourne) and run south through Corner Inlet's marked channels and out past Rabbit Island down the eastern Prom coast – about 30–40 km and 60–90 minutes to Sealers/Refuge Cove, longer to Waterloo Bay and South East Point. The coast is exposed to easterly and southerly swell and has no facilities; carry fuel, radio and all air, and plan around the weather window and Corner Inlet tides.

Larkin Cove is about 35 km from Port Welshpool between Refuge Cove and Brown Head; anchor in sand off the granite at 8–12 m. Shore access requires a long overland trek from the walking track and is impractical for scuba.

Best with calm seas, no swell or wind; light offshore south-westerly to south-easterly winds acceptable; avoid strong onshore northerly to easterly winds. The seaweed-floored cove silts easily, so visibility is best after several calm days. Autumn.

The eastern Prom coast is reached only after a long boat run from Port Welshpool, so the whole day's forecast must be settled: swell under 1–1.5 m, light winds, and no change due. Easterly and south-easterly swell is the main problem on this coast; a westerly wind flattens it but makes Corner Inlet's entrance choppy on the ebb. Visibility is typically 10–25 m and best in autumn after several calm days.

Descend onto the granite at the side of the cove and find the swim-throughs and caves at about 7 m – the main one is 12 m long – taking care to fin above the weed to avoid stirring silt; then follow the rock out to the seagrass edge and down to 15–25 m if wanted. Return through the shallows and finish under the boat.

No dive charter operates at Wilsons Promontory. Sites are dived from club and private trailer boats – Dive La Trobe, VSAG, Melbourne University Underwater Club and Dive Victoria Group run occasional camping-and-diving trips – launching at Tidal River (beach launch, permit/key from Parks Victoria), Port Welshpool or Sandy Point. Wilsons Promontory Cruises (Port Welshpool) runs sightseeing cruises to Skull Rock and the islands but no diving.