One of Australia's most beloved attractions is its 12 Apostles—ancient rock formations poking out of the waves off Victoria's coast. Scientists say they're in awe after discovering five "Drowned Apostles" in a linear formation hiding 160 feet underwater a few miles offshore. Melbourne University PhD student Rhiannon Bezore was studying a sonar scan of the area when she spotted what "looked suspiciously like sea stacks and I literally did a double take," she tells the Sydney Morning Herald. Colleague David Kennedy understands why. "This is the first time in the world we have seen underwater sea stacks," the geologist tells Reuters. "They don't last long due to erosion and according to all the textbooks they shouldn't be there."
Scientists believe the limestone columns have been around for 60,000 years—longer than the 12 Apostles, of which only eight remain—but broke apart from the cliff face, per a release. Kennedy believes the structures were drowned so quickly by rising seas around the end of the last ice age 11,000 years ago that "the waves just went over the top and they didn't have time to knock them over." The waves may have shortened the structures, though: The largest stretches about 32 feet high, while its neighbors closer to shore reach up to 130 feet high, per Reuters. The 12 Apostles are easier to visit since they don't require a wet suit, but they won't be around forever. Bezore warns they're eroding about 1 foot per year. (Scientists claim a new discovery about Stonehenge.)