Meet the site
The 20 Metre Ridge is an offshore reef north of Rottnest described by marinelife.org.au as a ridge at 20 m surrounded by a flat reef at 32 m, a couple of kilometres offshore. It is one of the deeper reef sites listed around the island, and the kind of site used by experienced Perth divers looking for bigger fish away from the busy inshore reefs.
Offshore ridges like this tend to attract demersal species such as dhufish and pink snapper, along with samson fish and kingfish in the water column, and the reef surfaces carry sponges, gorgonians and encrusting growth that are better developed than on shallow, surge-swept reefs. Visibility is often good because of the distance from shore.
With a minimum depth of 20 m and surrounding reef at 32 m, the site requires deep training or experience and careful attention to no-decompression limits; nitrox is recommended for the ridge and air or suitable nitrox for any excursion deeper.
It suits advanced divers with their own boat who are comfortable in open water and want a quieter, deeper reef dive within an hour of the metropolitan boat ramps. Leave a competent person on the boat, carry a DSMB and plan for current, which can pick up quickly on offshore reefs. Two short dives are better than one long one here, with a long surface interval between them.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
20 Metre Ridge is recorded as Reef in Rottnest Island. 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.
- Current and timing
- Ask how the operator assesses the current window for the actual route. Historical tide notes are not a departure instruction.
- 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 20 Metre Ridge 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 20 Metre Ridge 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
Dhufish, pink snapper, samson fish, yellowtail kingfish, buffalo bream, sponges, gorgonians
Location
Reef ridge at about 20 m surrounded by flat reef at 32 m, a couple of kilometres offshore north of Rottnest.
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.auRecord updated 26 Sept 2026. Source claims are being reviewed.