Meet the site
Carnac Island is a small limestone island and A-class nature reserve about 10 km off Fremantle. It is best known for its Australian sea lions, which haul out on its beaches, for its seabird colonies and for a large population of tiger snakes, which David Attenborough filmed for a documentary. For boaters, the sheltered eastern bay is a popular day anchorage for swimming and snorkelling.
For divers, the Marine Life Network describes the best reefs to the south and south-west: a weed-covered limestone reef about a mile wide with small caves that hold plenty of marine life. The Dark Cave area on the west side, about 14 m deep, has many sections of reef with caves and crevices. Schools of juvenile hammerhead sharks have been recorded in summer. Reef life includes buffalo bream, wrasse, sweep, herring cale and western rock lobster, and bottlenose dolphins are common.
The sea lions are the highlight for many visitors. They are mostly males resting between breeding seasons and may investigate snorkellers in the water. Keep at least 10 m away, never approach animals on the beach, and let them choose how close to come.
Visibility can be poor, and the outer reefs are exposed, so choose calm days. Landing is limited to the beach, the interior is closed and full of tiger snakes, and closures are applied at times for wildlife.
Carnac suits snorkellers and Open Water divers on calm days, and it makes an easy half-day trip from Fremantle. The run back to Fremantle can be rough once the afternoon sea breeze arrives, so plan to leave by early afternoon.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Carnac Island is recorded as Island in Perth. 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.
- Other water users
- Ask about vessel activity, exclusion areas and the agreed surface arrangements.
- Overhead environments
- Ask whether the plan stays entirely in open water. A wreck or cave listing is not permission or training to enter.
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 Carnac Island suitable for my certification?
The record lists 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 Carnac Island 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
Australian sea lions, bottlenose dolphins, juvenile hammerhead sharks (seasonal), buffalo bream, wrasse, sweep, herring cale, western rock lobster, little penguins, seabirds
Location
Limestone island nature reserve about 10 km south-west of Fremantle between Rottnest and Garden Island, with reefs on its south and south-west sides, caves on the west side and an Australian sea lion haul-out.
Facilities nearby
Woodman Point and Fremantle boat ramps; no facilities on the island.
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
marinelife.org.auperthisok.comweareexplorers.coRecord updated 26 Sept 2026. Source claims are being reviewed.
