Five Fathom Reef

Five Fathom Reef Dive Site Guide | Rockingham, WA, Australia

By ScubaDownUnder Team · 2026-04-14

# Five Fathom Reef

A submerged reef platform south of Rockingham in the Shoalwater Islands Marine Park, with resident weedy sea dragons, marine mammals from the nearby colonies, and a temperate southern WA reef community.

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## Quick stats

| Detail | Info | |---|---| | Location | Rockingham, WA | | Skill Level | Intermediate | | Depth Range | 6–18 m | | Typical Visibility | 5–18 m | | Water Temperature | 16–22 degrees C | | Best Season | November–April | | Entry Type | Boat | | Hazards | Boat traffic in Shoalwater Bay; Current around the reef on spring tides; Swell in the more exposed sections | | Facilities | Boat launch from Rockingham boat ramp or Palm Beach boat ramp; Full facilities in Rockingham |

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Five Fathom Reef sits within the Shoalwater Islands Marine Park south of Rockingham, in the arc of protected water that spans from the mainland out to Penguin Island and Seal Island. The reef itself is a submerged platform that rises to around 6 metres from an 18-metre surrounding depth, and its position within the marine park means the biological community on its surfaces has been developing under protection for decades.

The Shoalwater Islands Marine Park was established to protect the ecological values of an area that includes significant seabird and marine mammal populations alongside the reef and seagrass ecosystem of the inner coast. The nearby colonies on Seal Island and Penguin Island contribute their animals to the water around Five Fathom Reef regularly, Australian sea lions from Seal Island are a reliable presence, and little penguins are occasionally encountered in the water, swimming with an agility in their element that their waddling ashore entirely fails to suggest.

Weedy sea dragons are resident on the reef in the kelp and seagrass zones, and their presence in the temperate southern WA waters connects this site to the sea dragon community that runs along the continent's southern coast from SA across to WA. The nudibranchs on the encrusting reef surfaces reward a patient search, and wobbegong sharks rest on the reef structure in the characteristic flat, immobile posture of an ambush predator that has nowhere in particular to be.

Water temperature ranges from 16°C in winter to 22°C in summer, and a 5mm wetsuit is adequate for the warmer months. The proximity to Perth, 45 minutes by road to Rockingham, makes this one of the most logistically accessible southern WA reef dives available.

## Site Access and Logistics

Rockingham is approximately 45km south of Perth via the Kwinana Freeway. The reef requires a short boat trip from the Rockingham or Palm Beach boat ramp. Open Water certification appropriate. Book through Shoalwater-based operators for guided dives that also cover sea lion and penguin snorkelling.