Meet the site
The Chalmers was a 595-ton, 40 m three-masted timber barque sailing from Mauritius with sugar and 300 tons of ballast stones. On 19 March 1874 Captain W. R. Alexander, approaching what he believed was the safe passage into Fremantle north of Rottnest, mistook a bushfire on the mainland for the Rottnest lighthouse. The ship struck the reef once, but, confident of his position, he sailed on. After a second hard impact a third holed the hull. The captain's certificate was later cancelled indefinitely for negligence.
The wreck lies in about 3 m on the Sisters Reef in Warnbro Sound. After 150 years little structure remains. The main feature is a large kelp-covered mound marking the ballast pile, with ship's timbers, brass fittings and ballast stones scattered around it. Finding them takes patience and a slow search among the kelp, which is heavy in summer. The site is protected as a historic wreck.
The reef supports buffalo bream, wrasse, sweep and herring cale, and sea lions from the Shoalwater islands may visit.
The Chalmers suits snorkellers and divers interested in maritime history who can dive it together with the Sisters reef on a calm day. It is not a structural wreck dive, and divers expecting a hull will be disappointed. Its story, a ship lost because a bushfire was taken for a lighthouse, is a reminder of how dangerous this coast was before modern navigation aids. The WA Museum holds further records.
Because the site is so shallow, bottom time is limited only by air and warmth, and a slow, methodical search pattern around the ballast pile gives the best chance of spotting fittings. A torch helps to pick out brass and timber in the shade of the kelp.
Research this site before booking Stored site notes may be historical. These questions highlight gaps without turning old instructions into a current dive plan.
Chalmers Wreck is recorded as Wreck 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.
- 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 Chalmers Wreck suitable for my certification?
The record lists Snorkel/Any. 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 Chalmers Wreck 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
Buffalo bream, wrasse, sweep, herring cale, kelp, occasional sea lions
Location
Scattered remains and ballast mound of the timber barque Chalmers, wrecked in 1874, in 3 m on the Sisters Reef in Warnbro Sound.
Facilities nearby
Bent Street and Port Kennedy boat ramps.
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
divingwawrecks.comdivingwawrecks.comRecord updated 27 Sept 2026. Source claims are being reviewed.
