Meet the site
Keyhole takes its name from the shapes of its openings. Australia's Coral Coast describes it as a swim-through channel with overhangs in the shapes of windows and keyholes, and Travel2Next places it on the western side of South Muiron, with overhangs brimming with glassfish and an array of soft corals.
The structure is limestone reef undercut into overhangs, arches and short swim-throughs in roughly 8–20 m. Soft corals, sponges and gorgonian fans hang from the ceilings; glassfish and cardinalfish fill the shade; and cod, coral trout and wobbegongs rest in the recesses. Turtles, reef sharks and occasional mantas pass along the reef. The light shafts through the keyhole openings make it a favourite for wide-angle photography.
It is one of the most popular Muiron moorings and suitable for Open Water divers with good buoyancy. Being on the western side, it is exposed to south-westerly swell and is only dived when conditions allow.
The 2025 marine heatwave caused significant coral loss in the region and Dive Ningaloo paused Muiron trips; check with other operators.
About the Muirons: North and South Muiron are two low, uninhabited limestone islands about 15 km north-east of the tip of North West Cape, protected within the World Heritage-listed Muiron Islands Marine Management Area. They are reached only by boat, which has kept the surrounding reefs relatively untouched. The waters are visited by dolphins, dugong, pilot whales and, from July to October, migrating humpback whales, and turtles nest on the island beaches in summer. The islands are well known for strong currents and changeable conditions, so dives are always chosen on the day by the skipper according to wind, swell and tide, and a day on the Muirons usually combines two sites with lunch on the boat in the lee of the islands.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Keyhole is recorded as Reef in Ningaloo – Exmouth. 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.
- Water movement
- Ask how swell and local exposure affect the proposed entry, exit and route.
- 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 Keyhole 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 Keyhole 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
Glassfish, cardinalfish, soft corals, sponges, gorgonians, cod, coral trout, wobbegongs, turtles, reef sharks, manta rays (occasional)
Location
Reef on the western side of South Muiron Island with overhangs and a swim-through channel shaped like windows and keyholes.
Facilities nearby
Departure facilities at Exmouth Marina (toilets, fuel, parking) or Bundegi ramp; air fills in Exmouth.
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
travel2next.comdiveningaloo.com.auaussiemarineadventures.com.auaustraliascoralcoast.comsaltandcharcoal.coexploreparks.dbca.wa.gov.auRecord updated 27 Sept 2026. Source claims are being reviewed.