Jervoise Bay is a sea-wall and jetty dive that most Perth divers keep for days when everything else is closed. Man-made rock groynes and a concrete jetty protect the Cockburn Power Boat Club ramps on the south side of Woodman Point, and the water between them stays sheltered in weather that makes the open coast undiveable. Depth runs from the shallows to about 10 m along the outer walls.

The life is better than the setting suggests. Banded toadfish are everywhere and very curious. Colonies of zoanthids about a metre across cover some boulders, grey fan sponges 50–70 cm tall stand along the walls, and there are small corals, nudibranchs, filefish and leatherjackets. Giant cuttlefish are regular visitors, particularly in the cooler months, and the shallows under the concrete jetty are often the clearest part of the dive.

The drawbacks are real. The bottom is fine silt that clouds with one careless kick, so visibility of 3–4 m can drop to nothing behind a group. Entries and exits over the jagged rocks at the groyne corners need care, and an easy entry can become a hard exit if you surface in the wrong place. This is a working boat ramp, so stay out of the launch lanes and use a flag.

Jervoise Bay suits experienced shore divers with good buoyancy who want a dive on a windy day, and photographers after toadfish, zoanthids and cuttlefish. It is not a first choice for beginners or groups. Divers who log it regularly say the best results come from diving slowly in small buddy pairs, early on a weekday, before the ramp gets busy.

From Cockburn Road turn west towards Woodman Point and follow signs to the Cockburn Power Boat Club and the Jervoise Bay public boat ramps on the south side of the point. There is a large car park by the ramps; Howies notes an adjacent unsealed area was used by divers when the fenced area's status was unclear. Keep valuables hidden: the site is isolated on weekdays.

Enter from the small beach inside the rock groyne, from the concrete jetty area, or over the jagged rocks at the groyne corners. Choose an entry you can also exit from. About 20 minutes from Fremantle and Rockingham.

The sea walls and jetty create sheltered water between them, so this is one of the few places diveable in strong westerly or south-westerly winds that close the open coast. It is still affected by strong north-westerlies. Visibility is usually 3–4 m and depends mostly on how gently divers move, because the bottom is very fine silt.

Shallower water and the area under the concrete jetty are usually clearer. Avoid boat-ramp peak times on weekends and public holidays, when launches and retrievals are continuous.

Enter from the beach inside the groyne and follow the base of the rock wall seaward, where the depth increases to about 10 m. Look along the boulders for toadfish, zoanthids and fan sponges, then swing back under the concrete jetty in the shallows. Keep off the silt, stay clear of the ramp lanes and surface next to the wall.

No regular operator. An occasional bad-weather shore dive for local divers and clubs.