Cape Bridgewater is the great basalt and limestone headland west of Portland, and on its eastern side, below cliffs that reach 130 m, lives one of the few mainland colonies of Australian fur seals in Australia – several hundred animals, with long-nosed fur seals among them, hauled out on ledges and caves at the water's edge. The Scuba Doctor lists a boat dive site directly below the colony in 5–10 m, and the description is of playful, curious seals speeding past in what it calls an exciting and thrilling experience, over a reef of ledges, swim-throughs and kelp forests with abalone and crayfish in the cracks. The cliff continues underwater as a basalt wall and boulder slope with the heavy sponge and ascidian growth of the cold Bonney Upwelling water, and the fish are the western reef community – wrasse, sweep, magpie perch, morwong, leatherjackets – with schools of salmon and the occasional kingfish in summer. Horseshoe Reef and the SS Barwon wreck lie 1.5 km to the north in the calmer water near Fisherman Cove.

It is the most accessible seal dive in western Victoria for anyone with a boat: a ten-minute run from the beach ramp at Cape Bridgewater township on a calm day, Open Water depth, and seals guaranteed. Two cautions frame it. The Victorian wildlife regulations require boats to stay 50 m and swimmers 30 m from seals unless the animals approach, and the hauled-out animals should never be disturbed. And this is white shark country: the colony is a known feeding area, and Visit Portland's advice to avoid October to January, the pupping season, is sensible; most local divers go in autumn. No dive charter operates here – the Seals by Sea tour boats view the colony from the surface – so the dive is done from private boats or by arrangement, with Portland SCUBA the source of air and local advice. For those without a boat, the Seal Walk along the clifftop gives a view of the colony, and the Petrified Forest and Blowholes on the western side of the cape are worth the visit in themselves, though the western side lies within Discovery Bay Marine National Park and is a very different, fully exposed proposition.

From Portland drive 21 km west on the Bridgewater Road to Cape Bridgewater township on Bridgewater Bay, where a boat ramp on the beach launches small boats onto the bay (conditions-dependent); the colony is 2.5 km south along the eastern side of the cape, ten minutes by boat. Alternatively launch at the Portland Harbour ramps and run 20 km west around Cape Nelson, about 45 minutes. The colony can also be viewed from the Seal Walk, a 2 km clifftop track from the Blowholes car park, but there is no shore access to the water below the seals.

Keep the boat at least 50 m from hauled-out seals. Portland SCUBA supplies air; no dive charter operates in the area.

The colony is on the eastern side of Cape Bridgewater, sheltered from the prevailing westerlies by the cape, and the Scuba Doctor calls it weather-dependent, best in good conditions with low swell and light offshore westerly winds. It is open to the south-east and east, so any swell wrapping into Bridgewater Bay or an easterly wind makes the cliff base surge and the small Bridgewater ramp unusable. The Bonney Upwelling makes the water cold and rich from November to April – which is also the seal pupping season and the period Visit Portland advises avoiding because great white sharks frequent the colony.

Autumn gives the clearest water and the most settled seas.

Anchor on sand off the reef in 8–10 m, at least 50 m from the hauled-out seals, descend and work along the ledges, swim-throughs and kelp at the base of the cliff, letting the seals come to you in the shallows rather than approaching the rocks. Turn at half gas, return to the anchor and complete a slow ascent with the seals around the boat; do not surface close to the haul-out.

No dive charter. Cape Bridgewater seal-viewing boat tours (Seals by Sea) run from the beach in season and are the only regular vessels at the colony; divers use private boats from the Bridgewater ramp or Portland, or Portland SCUBA day trips by arrangement.