In September 2026, 20 Australian university students set out from Brisbane on a sea training voyage aboard the CSIRO research vessel RV Investigator. As part of the CAPSTAN program, the students were conducting underwater surveys of shipwrecks in the coastal waters off Queensland. During one of these surveys, they discovered something unusual: a shipwreck surrounded by a mysterious pattern of circular holes on the seafloor. The wreck they were mapping was the Althea II, a popular diving site located 40 meters (131 feet) beneath the surface off Bundaberg. Lara Picton, an honors geology student from the Queensland University of Technology, described the discovery as both surprising and exciting. "We initially saw a few depressions on the seafloor, but as we mapped the area, we realized the pattern was much more widespread," she said. "There were about 300 holes, each roughly 8 meters (26 feet) in diameter and 2 meters (7 feet) deep, extending up to 100 meters (328 feet) from the wreck in all directions." The team considered whether the holes might be the result of biological activity. To test this idea, they deployed a drop camera from the RV Investigator to gather footage of the site. The footage revealed a rich marine environment, including large fish like rockcod. The scientists suspected the holes were caused by bioturbation, a process in which marine organisms—such as fish and crustaceans—disturb and mix the sediment as they feed, move, or dig burrows. Maddison Cross, a marine biology Ph.D. candidate from the University of the Sunshine Coast, explained that such creatures act as "ecosystem engineers," reshaping the seafloor. "The consistent size and shape of the holes might be due to the natural preferences of the animals using them," she said. For example, goldspotted rockcod, a large predatory fish, may use the holes as shelters and hunting grounds. Interestingly, the area directly around the Althea II wreck had no holes, possibly because it is too dangerous for these animals due to the presence of predators on the wreck itself. Dr. Ben Arthur, the voyage manager for the CAPSTAN expedition, recalled a similar discovery from a past research voyage. In 2017, during a search for the wreck of the SS Macumba, a World War II-era merchant ship, the team had nearly given up on finding the wreck. However, an experienced biologist noticed a series of circular "pock marks" on the seafloor at the edge of the search area. These were likely caused by bioturbation, and the team decided to investigate further. This led them directly to the SS Macumba, which had been lost 74 years earlier. Arthur described the moment as a mix of relief and excitement. "Without those pock marks and the quick thinking of the crew, we might never have found the wreck," he said. Shipwrecks often become unexpected oases of life on the seafloor, creating what scientists call "shipwreck ecology." Dr. Arthur explained that these wrecks provide shelter and food for a wide range of marine life, from small crustaceans to large predatory fish. This biodiversity can make wrecks attractive to fishers, who often use the increased fish activity to locate the sites. In fact, the RV Investigator and its research teams have used this knowledge to identify several significant wrecks, including the MV Blythe Star in Tasmania and the MV Noongah in New South Wales. These discoveries highlight the value of combining scientific expertise, local knowledge, and advanced technology in uncovering the secrets of the deep.