Meet the site
The Swim Through is one of the named sections of the Lonsdale Wall cliff, sitting between Spot G and North Wall Corner on the northern part of the system. The Scuba Doctor listing gives a depth range of 20–30 m and describes it simply as 'yet another awesome dive site on Lonsdale Wall'; the name comes from a cleft where a slab of the limestone face has split away from the main wall, leaving a short passage that a diver can pass through from the terrace to the open face.
The topography is that of the whole wall in miniature. The reef top lies at about 20 m, covered in short kelp, sponges and bryozoans, and the lip falls away in steps with a deep overhang behind each. The swim-through itself is not a cave in the technical sense – there is daylight at both ends and no silt – but it is dark enough inside to need a torch, and the walls of the passage are plastered with the yellow zoanthids, jewel anemones and orange sponges that characterise the Heads. Blue devils and southern rock lobster use the passage as shelter, and old wives and boarfish hang in the eddy at its mouth.
Because it lies in the 20–30 m band, this is one of the more comfortable deep sections of the wall for Advanced divers: there is a defined feature to visit, a natural turn-around point, and no need to go past 30 m to see the best of it. Operators pair it with Spot G, which is only 12 m away along the face, and a diver may well cover both on the same slack. As with every site on this wall, the entire dive happens inside the slack-water window and ends with a drift under a DSMB.
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 Swim Through is recorded as Wall in Port Phillip Heads. 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.
- Water movement
- Ask how swell and local exposure affect the proposed entry, exit and route.
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 Swim Through 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 The Swim Through 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
Yellow zoanthids, jewel anemones, sponges, southern blue devil, southern rock lobster, old wife, longsnout boarfish, magpie perch, nudibranchs
Location
On the Lonsdale Wall system just inside the Heads, 36 m west of North Wall Corner and 12 m from Spot G.
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.auscubadoctor.com.auscubadoctor.com.auRecord updated 26 Sept 2026. Source claims are being reviewed.
