Blue Bay is one of the best-known snorkelling and shore-dive spots in Mandurah, on the Halls Head coast south of the marina. Tourism guides describe calm conditions, colourful fish and rock pools at low tide, and the Marine Life Network describes great swim-throughs and caves with interesting small marine life in 4–8 m.

The reef is limestone, weathered into ledges, small caves and swim-throughs close to shore. Wrasse, buffalo bream, sweep, herring cale, leatherjackets and small reef fish are common, and divers searching slowly find nudibranchs, octopus, crabs and sea stars. The rock pools are good for children at low tide.

The site is relatively exposed, and visibility drops after swells above 1 m, so pick a calm day. Entry and exit are easy, but take care on the beach steps.

Blue Bay suits families, snorkellers and beginner divers, and it is Mandurah's most accessible reef dive. Combined with Roberts Point to the north, it gives a good morning of shore diving without a boat.

The Scuba Directory lists Blue Bay Reef as a boat site, but other sources describe shore access. Its coordinates should be confirmed.

The bay is popular with swimmers and families on summer weekends, so divers should use a flag, stay aware of people in the water and avoid the busiest hours. Early mornings are usually calmest and clearest. Divers wanting more depth can combine a morning here with a boat trip to the Murray Reefs or the James Service wreck offshore, both reached from the Mandurah ramps in 15–20 minutes. Water temperatures follow the Perth pattern, from about 17 °C in winter to 22–23 °C in late summer.

From central Mandurah cross the estuary to Halls Head and follow the coastal roads south to Blue Bay, about 13 minutes' drive. Park at the beach car park, which has showers and toilets nearby. Take care on the beach steps, then enter from the sand; the reef is close to shore.

There is little shade, so bring sun protection. Allow about an hour from Perth via the Kwinana Freeway.

Relatively exposed to westerly swell; visibility is poor after swells over 1 m. The bay is calm on still mornings and in easterly weather, and rock pools can be explored at low tide. Mandurah's summer south-westerly sea breeze usually arrives around midday.

North-westerly winds ahead of winter fronts close the site. Avoid the days after heavy rain, when runoff reduces visibility.

Enter from the sand and swim out to the reef, descend in 3–4 m and explore the swim-throughs and caves along the reef to about 8 m, then return along the inshore edge.

No regular operator; popular with local divers and snorkellers.