Meet the site
The Keyhole is described by the Marine Life Network as one of the best deep sites at Montague Island. It lies west of the seal colony, with deep sponge gardens from 20 to 40 m featuring large sea fans and schools of pelagic fish. That places it in the zone below the kelp, where rock surfaces are covered in filter feeders and the open-water location attracts fish.
Expect large gorgonian sea fans, sponges of many shapes and colours, sea whips and sea squirts, with bullseyes, nannygai and red morwong on the reef and schools of yellowtail, silver trevally and kingfish in the water column. Being close to the seal colony, divers often have seals for company, and grey nurse sharks from the northern gutters may pass through in summer. Visibility is often good at this depth when the East Australian Current pushes warm blue water south.
This is a deep dive: at 30–40 m, air no-decompression limits are very short and narcosis is significant, so it suits Deep-certified divers with experience, ideally on nitrox or with technical training for the deeper parts. The name suggests a hole or gap in the reef, but no published description explains it. The position is not published, so dive with a Narooma operator. Sharks, including great whites, are occasionally seen near seal colonies, so follow the operator's briefing. Because the site is used only when conditions are right, ask the operator in advance whether a deep day is planned and bring nitrox certification if you have it. A torch or strobe brings out the reds and oranges of the sea fans, which look grey-blue in natural light at this depth.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
The Keyhole (Montague Island) is recorded as Reef in Narooma & Montague 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 The Keyhole (Montague Island) 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 The Keyhole (Montague 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
Gorgonian sea fans, sponges, sea whips, sea squirts, bullseyes, nannygai, red morwong, yellowtail, silver trevally, kingfish, fur seals, grey nurse sharks (seasonal)
Location
Deep sponge gardens west of the Montague seal colony with large sea fans and schools of pelagic fish; 20–40 m.
Facilities nearby
Narooma town wharf and marina.
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.