Shark Bay was a desert plain until rising sea levels at the end of the last Ice Age flooded it roughly 8,000 years ago. Aboriginal peoples had lived in this landscape for at least 22,000 years before the water came. Today the bay is divided by the long Peron Peninsula, with the resort towns of Denham (population 754) and Monkey Mia at its tip. East of the peninsula, a shallow sandbar partitions the inlet further, creating two hypersaline lagoons with habitats found almost nowhere else. Shell Beach, at the pinch point of Taillefer Isthmus, is exactly what its name promises: 60 km of coastline composed entirely of cockle shells, up to 10 meters deep. The shells accumulate because L'Haridon Bight is too calm for waves to pulverize them and too salty for the crabs and fish that would normally eat the cockles. They were once quarried for lime.

The bay's population of around 2,000 Indo-Pacific bottlenose dolphins has been the subject of one of the longest-running marine mammal studies in the world. Researchers have documented the dolphins' family structures, maternal behavior, and -- most remarkably -- their use of marine sponges as foraging tools, carrying them on their snouts to probe the sandy seabed for hidden prey. At Monkey Mia, five specific known individuals come inshore to be hand-fed by rangers each morning, a tradition that draws visitors from across the globe. Beyond the dolphins, dugongs graze on the vast Wooramel Seagrass Bank -- an underwater prairie 130 km long and 8 km wide that shelters the inner lagoon and renders it hypersaline. The water is too warm for coral, but the seagrass traps calcium carbonate from the remains of crabs and shellfish, building a biological reef of a different kind.

In Hamelin Pool, the larger eastern lagoon, the extreme salinity has protected something extraordinary: living stromatolites, layered mounds of cyanobacteria, sand, and shell fragments that resemble structures found in the fossil record dating back 3.5 billion years. These are among the oldest living structures on Earth. The cyanobacteria that build them are descendants of organisms that oxygenated the early atmosphere long before plants existed. Nearby, the Hamelin Pool Telegraph Station -- built in 1884 -- has been converted into a museum with what is said to be the world's only captive stromatolite, kept alive in an aquarium. A boardwalk allows visitors to view the formations without disturbing them. They grow at roughly 0.5 mm per year; a careless footprint can destroy centuries of accumulation.

Dirk Hartog arrived in 1616, found nothing to interest the Dutch East India Company, and sailed on -- but not before nailing a pewter dinner plate to a post on the island that now bears his name. Francois Peron collected over 100,000 wildlife specimens during an 1801-03 expedition. The shores and islands were eventually turned over to sheep and goat farming, pearl fishing, salt production, and lime quarrying. From the 1990s, the government began buying out pastoral leases and restoring native habitats. Francois Peron National Park now covers the peninsula that the Malgana people call Wulyibidi, and Dirk Hartog Island is undergoing its own ambitious rewilding program. Not every restoration has succeeded: an attempt to re-wild Heirisson Prong near the salt-mining town of Useless Loop was abandoned in 2013 after removing foxes caused the feral cat population to soar, and killing cats let the rabbits proliferate.

Shark Bay is a place defined by extremes of heat and distance. Summer temperatures can be brutal, and Denham is the only settlement with a fuel station for 140 km in any direction. Mobile coverage barely exists beyond the town center. Four-wheel-drive is required for the national park's sandy tracks. Steep Point, the most westerly point on the Australian mainland at 113.156 degrees east, lies at the bay's edge -- placing you on the same longitude as Guangzhou. Bernier and Dorre Islands to the north carry a dark history: from 1908 to 1909, Aboriginal people suspected of having venereal disease were forcibly interned there, men on one island, women and children on the other. Today the islands are wildlife reserves. The bay's quieter pleasures are its own: emus amble across the beach at Monkey Mia, sharks cruise the shallows at Skipjack Point, and the salt mountain at Useless Loop -- 1.4 million tonnes of annual production -- glitters like snow from across the water.