Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: It may look like a run-of-the mill paddock, but beneath the surface lies a breath-taking phenomenon. Situated 450 km southeast of Adelaide is Mount Gambier, one of the few places in the world with the water conditions and soft limestone bedrock that give rise to spectacular underground sinkholes. Stunning images show specialist divers exploring otherworldly sites such as the 65 metre deep Kilsby’s Sinkhole and the 120 metre deep Shaft, which lie below seemingly mundane farms and paddocks. The caverns are the epicentre of The Cave Divers Association of Australia, who navigate the sites in the name of science. ‘Most people are drawn to the sport for the challenge and exploration, but they become passionate about the scientific elements afterwards,’ said John Vanderleest, the national director of the Cave Divers Association of Australia.Mount Gambier is one of the few cities in the world with the right conditions for underground sinkholesIt features spectacular sites like Kilsby’s Sinkhole and the The Shaft, which are found below paddocksThe caverns are among 30 identified cave sites used by the The Cave Divers Association of AustraliaCave diving involves rigorous training to explore elusive caves using specified gear and equiptment 
 Question:_ use scuba gear and harnesses to traverse the caverns and unearth marine life and geographic discoveries.

The Cave Divers Association of Australia