GPS: S 32° 22.030'
E 115° 41.437'
Location: The Sisters Reef, Warnbro Sound
Site depth: 3 metres
Divable conditions: Swell less than 1.5 metres
Visibilty: 5-10 metres
Vessel: 3 masted barque
Tons: 595 tons
Vessel length: 40 metres
Wreck event: Wrecked on shallow reef 1874.
The Chalmers was wrecked on the 19th of March 1874 as the Captain approached what he thought was a safe passage into Fremantle Port north of Rottnest. The Chalmers had sailed from Mauritius with a cargo of sugar and 300 tons of ballast stones. On the evening of the 19th Captain W.R. Alexander approached Fremantle thinking his ship was north of Rottnest Island when both the mate and the captain himself sighted what they thought was a revolving light of the Rottnest lighthouse. The light which had been sighted was in fact a bushfire burning on the mainland, the Chalmers held it's south east course and when it first grazed the reef the Captain was so confident of his position that he continued sailing, assuming the collision was drifting wreckage. 10 minutes later, the 595 ton barque struck again hard against Murray Reef south of Rockingham, the sails were shortened and boat launched to try and kedge the stricken ship off the reef. The vessel was pulled clear of the reef just as dawn broke and just as the sails were being reset through a clear passage, the wind shifted driving the Chalmers back onto another reef where it was quickly holed and began to fill with water. Captain Alexander was charged with negligence resulting in the loss of his ship, he was stripped of his certificate indefinitely due to his lack of action in determining his position and his failure to respond after the Chalmers hit the reef for the first time.
The site of the Chalmers is located on the inside of the Murray Reefs south of "The Sisters" rocks off Warnbro Sound. By boat, the site is easily accessible from both the Bent St boat ramp and the Port Kennedy boat ramp, a short trip of less than 10 minutes from both. The site is exposed to the seabreeze and only somewhat protected from swell so any winds over 15 knots and swell over 1.5 metres would make the site difficult to reach.
The site is quite shallow and heavily overgrown with kelp and seaweed, very little remains structurally of the wreck however, scattered around the seafloor are numerous brass fittings, ships timbers and ballast stones all visible if shifting aside the thick kelp. Almost right under the GPS mark is a large kelp covered mound, this is the central point of the wreck site, it is most likely the ballast cargo pile that has been reclaimed by the reef and kelp, scattered around the mound is where most of the wreck debris can be found. The site needs a bit of a trained eye to see what is what, square stones that sit out of place amongst the limestone seascape, buried timbers and small shards of hull sheating all give a great representation of what a wooden sailing shipwreck site look like after a century and a half underwater. Just to the south of the mound, a smaller lump of kelp shown in the background image is actually the heavily overgrown museum plinth that was put on the site in the early 90's.