Meet the site
Four Mile Reef is the main natural reef dive out of Busselton and a good counterpoint to the jetty. Swan Dive describes it as a 15-20 m site that is full of life, with large corals, schools of fish and tiny nudibranchs, and lists starfish, turtles and coral formations among the sightings. Octopus Garden Dive Charters in Bunbury also lists 'Busselton 4-mile reef' at 15-18 m. The name reflects its distance offshore in Geographe Bay.
The reef is part of the extensive system of limestone reefs and seagrass that makes Geographe Bay one of the richest temperate bays in Australia, influenced by the warm Leeuwin Current. Coral cover here is unusually good for a temperate site, and the sponges and ascidians attract a variety of nudibranchs, which makes it popular with macro photographers. Schooling fish such as bullseyes and buffalo bream, and western blue devils and wrasse, are common.
Swan Dive requires divers to be Open Water certified, to have dived in the past 12 months and to carry a DSMB and reel, reflecting the offshore setting and the risk of surfacing away from the boat. It suits Open Water divers who want a genuine reef dive near Busselton and is often combined with the HMAS Swan on a double-dive day.
Early starts are the norm because the sea breeze usually arrives by late morning.
Geographe Bay is unusual on the WA coast because it faces north, so the prevailing south-westerly swell and sea breeze that close the ocean coast are largely blocked by Cape Naturaliste. That shelter, plus the warm Leeuwin Current, is what makes the bay's reefs, jetties and wrecks diveable for much of the year, and why winter north-westerly storms are the main thing that shuts it down.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Four Mile Reef is recorded as Reef in Geographe Bay & Busselton. The listed access is boat (day trip). Confirm the actual meeting point, route and permission to visit; a map pin does not establish any of these.
Topics flagged by the stored research
These are questions prompted by the existing notes, not a verified or complete hazard assessment.
- Other water users
- Ask about vessel activity, exclusion areas and the agreed surface arrangements.
Historical access notes exist for this record, but have not been independently verified for current use. Request current directions from the operator or site manager rather than following an old entry description.
Questions, answered
Is Four Mile Reef suitable for my certification?
The record lists Advanced Open Water. That does not establish suitability for every route or day. Share your training, recent experience and equipment needs with the operator and ask about the specific proposed dive.
Can I book Four Mile Reef through YouDive?
YouDive is an independent research directory. Contact an operator directly to confirm whether it currently runs the trip, the inclusions and the booking terms.
What you might see
Hard corals, sponges, nudibranchs, western blue devil, bullseyes, buffalo bream, western king wrasse, starfish, turtles (occasional)
Location
Offshore Geographe Bay reef in 15-20 m reached by boat from the Busselton foreshore past the jetty, with large corals, schooling fish and nudibranchs.
Facilities nearby
Swan Dive shop (hire, fills, nitrox) at Busselton; foreshore facilities.
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
swandive.com.auswandive.com.auoctopusgardendivecharters.com.auRecord updated 27 Sept 2026. Source claims are being reviewed.