Trigg Beach is one of Perth's best-known surf breaks, and the limestone reef just offshore is a rewarding dive on the rare days when the ocean is flat. The reef runs about 250 m north to south, rising from a sandy bottom and deepening seaward from about 1 m near shore to around 6–7 m. It has reef walls, overhangs, ledges and small swim-throughs, particularly at the southern end.

Life is typical of the Sunset Coast's shallow reefs. Juvenile King George whiting are abundant over the sand, bream feed in the surge, boxfish and scalyfin shelter under the ledges, and a school of red-lipped morwong lives on the reef, along with weedfish, wrasse and sea stars. Bennion Beach, just north, has similar rocky ledges and reefy patches.

The challenge is conditions. Howies emphasises that it needs perfect weather, and the Marine Life Network says heavy swell pounding the beach makes it dangerous. The southern end has rips and undertow that can pull divers seaward quickly, so enter and exit at the north end. There is no dive flag, and surfers and boats use the area.

Trigg suits experienced shore divers who watch the forecast and can take advantage of a glassy morning. On those days it offers some of the best reef structure on the northern metro coast within walking distance of a car park.

Water temperatures on this coast range from about 17 °C in late winter to 22–23 °C in late summer, when the warm Leeuwin Current is strongest, so a 5 mm wetsuit suits summer and a 7 mm suit with a hood is more comfortable from June to October.

From the Mitchell Freeway exit at Karrinyup Road and follow it west to the roundabout at Trigg Place (West Coast Drive); turn left, then first right into the car park. Do final checks in the car park, then walk about 60 m to the beach. The main entry is at the north end via the Esplanade; the south end by the surf beach is an alternative entry but a hazardous exit because of rips.

About 15–20 minutes from the Perth CBD.

Trigg is a surf beach: any swell and it is a washout. It needs conditions as flat as possible, with swell under 1 m, a period around 11 seconds and gentle easterlies sustained for at least 24 hours. Winter dives are problematic even with good forecasts.

Rips and undertow form at the southern end. Dive early before the summer sea breeze.

Enter at the north end, swim out over sand to the reef and follow it south along its 250 m length, exploring ledges, overhangs and swim-throughs in 4–6 m. Turn before the southern surf area and return north, exiting where you entered. If caught in the rip at the south end, keep your regulator in and swim north-east over the reef.

No regular operator; dived independently on rare flat days.