A hidden world beneath the range
Beneath the arid limestone of Western Australia's Cape Range peninsula exists a hidden aquatic world. This is not a single underground river, but a network of more than 580 known caves and countless smaller voids filled with groundwater. The peninsula itself is an anticline, a ridge of limestone layers that were once an ancient seabed, tectonically uplifted over millions of years. This geological structure creates isolated pockets of water, some fresh and some brackish, effectively forming a subterranean archipelago. Each "island" of water is a discrete evolutionary laboratory, supporting unique life forms. This entire ecosystem is dependent on a lens of fresh groundwater floating on top of saltwater that permeates the porous limestone.
The inhabitants of this world are known as stygofauna, animals that live their entire lives in groundwater. They are relicts from a different era, their ancestors having populated the ancient Tethys Sea before becoming trapped in these underground reservoirs as the sea receded. Cut off from the outside world and from each other, they have evolved in complete darkness for millions of years. This isolation has led to biodiversity, with at least 69 subterranean species identified on the Exmouth Peninsula alone. Many of these show extreme adaptations to their environment, such as a lack of eyes and pigmentation, and heightened non-visual senses.