Ruthless, murderous and cruel yet charismatic and passionate, Black Jack Anderson ruled the islands and waters off WA's Recherche Archipelago in the early 1800s.

He is Australia's only known pirate, yet the story of his life and crimes is little known outside of Esperance, the south coast town closest to Anderson's hunting ground.

WA archaeologists, who went to Middle Island - the biggest island in the archipelago - during a recent expedition to the remote area, surveyed what is believed to have been Anderson's cave in a bay on the south side of the island.

Facing open ocean that stretches to Antarctica, "Black Jack's bay" can only be accessed in good weather, conditions that are not common in the wild Southern Ocean.

The limestone cave, which leads to chambers and tunnels that go deep into the ridge, is the perfect place for a pirate to hide his loot, as local legend has it.

Anderson was an American who came to Australia as his countrymen and Europeans hunted for seals and whales in the bountiful Southern Ocean.

He roamed the waters around Middle Island, robbing passing boats and ships. Anderson was reported to have killed local Aboriginal people and kidnapped women to live with, and serve, him and his followers.

Maritime archaeologist Ross Anderson, curator of WA Maritime Museum, said newspapers at the time warned of a band of pirates in the Recherche Archipelago.

"He seemed to be quite a charismatic leader so he had a little gang," Mr Anderson, who visited Middle Island with heritage group the Gabbie Kylie Foundation, said.

"He went out sealing and ruled by violence."

Transcribed copies of declarations made in Albany courthouse in September 1835 reveal that Middle Island was "in the possession of John Anderson, a master of a sealing boat".

The court also heard that Anderson stole money from seamen or forced them to give it to him or be murdered.

In October 1835, the Perth Gazette reported how Anderson and others shot and clubbed Aboriginal men to death and took the women in their boats.

"Two of the women had infants at their breasts at the time their husbands were murdered; an old woman was compelled to take them away, and carried them into the bush," the newspaper said.

Anderson is thought to be buried somewhere on Middle Island after members of his crew murdered him.

The remote cave contains enough sandy deposits to do an exploratory excavation in the hope of finding evidence of sealers and whalers, including the pirate and his crew.

Applied Archaeology Australia managing director David Guilfoyle said they also believed indigenous people could have used the cave thousands of years ago when sea levels were much lower than today and the cave was in a wooded area.

"Sheltered caves are generally excellent in the preservation of cultural material and organics, and regular deposition may 'trap' different periods of time," he said.

Given local legend says the cave was used by Anderson, Mr Guilfoyle said other people had searched there for the pirate's loot and he expected obvious artefacts to have been illegally removed or disturbed naturally.

The archaeologists plan to excavate the cave and other locations on Middle Island next year.