Meet the site
Crawfish Rock is one of the most remarkable and least-known dive sites in Victoria: a rock that shows at low tide in the middle of the North Arm of Western Port, off the north-western tip of French Island, whose sides plunge to 32 m on one face and 26 m on the French Island side into deep reefs, pinnacles, canyons and underwater channels. The deep water and the scouring tidal current keep sand and gravel from settling, and the result is a vertical garden of filter feeders of a richness found nowhere else in the bay – The Scuba Doctor describes a notably high invertebrate diversity and a unique and vulnerable marine community, home to threatened hydroids and other listed species, and the site is protected as a threatened community under Victoria's Flora and Fauna Guarantee Act. The walls are covered in sponges of every form and colour, soft corals, gorgonians, bryozoans, hydroid trees, ascidians and sea whips, with rock lobsters (the 'crawfish' of the name), blue devils, boarfish, morwong, wrasse and schooling sweep and trevally along the faces, and rays and draughtboard sharks on the sand at the foot. It has been studied by marine scientists since the 1960s as the outstanding example of Western Port's deep-channel sponge communities, and its decline and partial recovery have tracked the health of the bay. Diving it is a serious exercise in tidal planning: the current is strong and reversing, slack lasts minutes rather than hours, the depth is technical-adjacent, and the visibility is estuarine. It belongs to experienced club divers with a capable boat, a skipper who understands Western Port, and a conservative plan; anchoring on the rock is prohibited. For those who manage it, Crawfish Rock is a glimpse of the invertebrate wealth that made Western Port a Ramsar wetland, and one of the great hidden dives of the state.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Crawfish Rock is recorded as Pinnacle/Bommie in Mornington Peninsula. The listed access is boat. 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.
- Current and timing
- Ask how the operator assesses the current window for the actual route. Historical tide notes are not a departure instruction.
- Other water users
- Ask about vessel activity, exclusion areas and the agreed surface arrangements.
- Planned depth
- Confirm the intended route and training requirements; the recorded maximum is not a target.
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 Crawfish Rock suitable for my certification?
The record lists Deep/Advanced + experience. 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 Crawfish Rock 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
Sponges (exceptional diversity), hydroids including threatened species, soft corals, gorgonians, sea whips, bryozoans, ascidians, southern rock lobster, southern blue devil, long-snouted boarfish, dusky morwong, bluethroat wrasse, sea sweep, silver trevally, draughtboard shark, rays
Location
Rock exposed at low tide in the main tidal channel of Western Port's North Arm, 1.5 km north of Scrub Point off the north-western tip of French Island, dropping to 32 m on one side and 26 m on the French Island side.
Facilities nearby
Boat ramps at Warneet, Hastings, Stony Point and Somers; no facilities on site; nearest air fills at Frankston (Aquability, Diveline).
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
scubadoctor.com.auRecord updated 26 Sept 2026. Source claims are being reviewed.