As of 2014 the Royal Australian Navy operated an acoustic range, the South Australian Acoustic Range (SAAR), to help develop sonar techniques for submarines in the waters west of Thistle Island, with a small control facility being located on the island itself.

It was speculated that the remains, which "the ruins of some cottages with signs of regular order in their arrangement and a cleared promenade between them, all the loose limestone for a distance of a bout 100 yards having been thrown on each side of a broad path."

[12] In 1932, J. T. Mortlock gave an account from Whaler's Bay of the "mournful symphony of the curlews and penguins in the nearby cliffs".

[13] An account of a visit in 1928 wrote: "On Black Rock, at the north end of Thistle Island, we disturbed a large colony of seals, which rapidly scrambled into the water as the yacht passed by.

Many types of sea fowl were observed, including gannet, arctic skua, mollyhawk and stormy petrel.

"[14] Former Lord Mayor of Adelaide A. S. Hawker held a fishing record for a 47-pound (21 kg) tuna that he caught off Thistle Island in the late 1930s.

[18] By October 2020, the population was thriving so well on Thistle Island that it was possible to trap nine bilbies for relocation to the Arid Recovery Reserve near Roxby Downs, to help boost the gene pool there.