Kanowna Island is the largest of the Anser Group, the cluster of granite islands off the south-western tip of Wilsons Promontory, and it holds a breeding colony of more than 9,000 Australian fur seals with a smaller number of New Zealand fur seals. Scuba Doctor lists three dives around it; this one, on the southern side, is the seal dive. The listing describes it simply: there are so many playful and curious seals that diving with them becomes an exciting and thrilling experience.

The underwater terrain is a steep granite slope of boulders and ledges, thickly covered in various kelps in the shallows, forming crevices and gullies that are interesting to explore, and reaching about 25 m before the rock gives way to sand and the bottom falls away to 50 m nearby. In practice the dive happens in the top 20 m, where the light is good and the seals are. Juveniles and females peel off the haul-out rocks in groups, corkscrew around divers, blow bubbles in masks and hang upside down in the kelp watching, and a diver who stays still in a gully will be visited continuously.

Below the kelp the granite carries sponge, ascidian and bryozoan cover, with crayfish in the deeper ledges, and the fish are the exposed-reef community of the southern Prom – sweep, butterfly perch, wrasse, morwong and leatherjackets. Visibility is usually excellent. Great white sharks are attracted to the colony, particularly in autumn and winter, and every diver here accepts that.

The island is within the Wilsons Promontory Marine National Park, and the seal colony is protected by vessel exclusion zones that expand during the November–January breeding season; the exact distances are stated differently by different sources and must be checked with Parks Victoria before a trip. Combined with the 12 km run from Tidal River or the long passage around from Port Welshpool, that makes Kanowna an expedition dive done by a few club and private boats each year. For those who get there on a calm day it is Victoria's best seal dive – more seals, clearer water and wilder scenery than Seal Rocks or Montague Island.

Boat only. The nearest launch is the Tidal River beach ramp at the western end of Norman Bay (4WD beach launch, key and deposit from the Parks Victoria office; needs several people and calm surf), from which the western islands are 5–12 km. Larger trailer boats launch at Port Welshpool (sealed ramp, Corner Inlet) and run about 50–60 km around South East Point – 1.5–2 hours – or at Sandy Point (Waratah Bay, beach ramp) and run 35–45 km south-east.

Sites are exposed to Bass Strait and require settled weather, a seaworthy boat, radio, and self-sufficiency: there is no rescue or refuelling closer than Port Welshpool. Kanowna is about 12 km south of Tidal River and 50 km from Port Welshpool. Vessel exclusion zones apply around the island because of the seal breeding colony – Scuba Doctor cites 200 m in November–January and 50 m otherwise, while the Parks Victoria park note cites one nautical mile in November–January and 500 m otherwise – so check the current Parks Victoria rules before planning; divers may swim in from outside the zone.

Best with calm seas, no swell and no wind; light offshore north-west to south-west winds may be acceptable on this southern side, which is otherwise exposed to the full Bass Strait swell. Slack water is advisable because current runs between the Anser Islands. The rocky slope is surgy in any swell.

Seal numbers and activity peak in summer after the November–January pupping season, which is also when the vessel exclusion is largest. Late summer and autumn give the most settled days.

Anchor or hold the boat outside the exclusion zone on the lee side and swim in over the kelp to the rocky slope at 10–20 m. Settle in a gully and let the seals come; drift slowly along the slope with the island on one shoulder, staying above 25 m where the rock gives way to sand and the bottom falls to 50 m. Turn at half gas, retrace along the slope and ascend under an SMB for pick-up.

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.