Cottesloe Beach is Perth's most famous beach, and the reef system just offshore was declared the Cottesloe Reef Fish Habitat Protection Area in 2001, one of the first such areas in WA. The protection area covers the inshore reefs from North Cottesloe to South Cottesloe and aims to conserve fish habitat while allowing recreational use. Some fishing is permitted under specific rules, but the main uses are swimming, snorkelling and diving.

The inshore reef is limestone, weathered into ledges, gutters, pools and low overhangs covered in algae and seagrass edges. Well-known entry points include Peters Pool, a sandy lagoon ringed by reef at the end of Napier Street, the reef around the historic pylon off the main beach, and Marine Beach (Elizabeth Reef) at South Cottesloe. Offshore, deeper reefs extend towards Gage Roads and are reached by boat.

Fish life is good for a city beach. Divers see toadfish, striped grunter, whiting, damselfish, monocle bream, gold-lined bream, goatfish, leatherjackets, old wives, red-lipped and dusky morwong, silver drummer, stripeys and wrasse, with rays, sea hares and octopus on the sand and reef. In summer the eco shark barrier off the main beach develops its own marine growth.

The reef is shallow and exposed to westerly swell, so good days come after spells of easterly weather. Mornings are best, before the sea breeze and the crowds. The site suits snorkellers and new divers, and anyone wanting a reef dive without leaving the city. Divers wanting more depth can arrange a boat dive to the outer reefs from Fremantle.

Cottesloe is about 20 minutes west of the Perth CBD via Stirling Highway or Curtin Avenue, and Cottesloe train station is a 10-minute walk from the beach. Park along Marine Parade (paid and time-limited, busy on summer weekends). Shore divers and snorkellers enter from Peters Pool (end of Napier Street, North Cottesloe), the main beach near the Indiana tea house and the pylon, or South Cottesloe (Marine Beach).

Boats for the outer reefs launch at Fremantle or Hillarys.

Perth's northern coast is far more exposed to ocean swell than the Cockburn Sound sites. Cottesloe faces west into Gage Roads, partly sheltered by Rottnest, but westerly swell over about 1 m and onshore winds quickly stir the reef. Easterly or light winds give the best conditions; the south-westerly sea breeze usually worsens visibility by midday in summer, so go early.

Currents can push snorkellers around near tide changes. Winter fronts bring large swell and storms.

From the beach, swim out over sand to the nearest reef edge and follow its ledges and gutters in 2–5 m, turning at a landmark and returning parallel to shore. Stay well inside the surf zone in any swell.

No regular dive charters; the inshore reef is dived and snorkelled independently. Occasional guided snorkel sessions by local groups.