The Gulf is enormous and strangely flat. At its mouth it spans 590 kilometres, widening to 675 further south, and it runs more than 700 kilometres from north to south, covering roughly 300,000 square kilometres of sea. Yet it is barely a puddle by ocean standards: most of it is only 55 to 70 metres deep. The land that frames it is low and unbroken, with no mountain range to catch the rain. Because of that, the lush tropical growth of the coast fades into the dry scrub of central Australia not as a sharp line but as a slow, almost imperceptible drying-out of the country. Twice a day the tide moves across this huge shallow basin, rising and falling by two to three metres and breathing water deep into the rivers and mangroves of the surrounding Gulf Country.

The Morning Glory forms when sea breezes blowing off the Gulf and the Coral Sea collide over Cape York. As night air cools and collapses, it sends a solitary wave rolling across the Gulf, made visible as that astonishing cylinder of cloud, one to two kilometres high and travelling at up to forty kilometres an hour. The Gulf is the only place on Earth where it can be predicted with any confidence, and each spring a small band of glider pilots gathers at Burketown to ride the invisible wave at its leading edge, lifting silently along the front. As one pilot put it, fewer people have surfed the Morning Glory than have climbed Mount Everest.

Long before any of this had a European name, the Gulf and its country were home to peoples whose languages still map the land. Yulluna, also written Yalarnga, belongs to the Cloncurry region; Kayardild is the tongue of Bentinck Island and the Wellesley group. The European chapter opened in 1606 when the Dutchman Willem Janszoon became the first to chart this coast, the first recorded European to land in Australia at all. His countryman Jan Carstenszoon followed in 1623 and named the gulf for Pieter de Carpentier, then governor-general of the Dutch East Indies. Abel Tasman traced the coast in 1644; Matthew Flinders charted it in 1802 and 1803. The first Europeans to reach it overland, Burke and Wills, struggled to the mouth of the Bynoe River in 1861, then died on the journey home.

For all its emptiness, the Gulf is one of Australia's great working waters. Its real treasure swims unseen: the prawns. The Northern Prawn Fishery, one of the country's most valuable, depends on the Gulf, which supplies on average around 65 percent of its banana prawn catch and the overwhelming majority of its tiger prawns. Beneath the surface lies a geological surprise, a submerged province of coral reefs covering at least 300 square kilometres in the southern Gulf, undetected until sonar surveys revealed it in the mid-2000s, a fossil reef grown in an ice-age world of cooler seas and lower water. Above the seabed, zinc and lead from inland mines ship out through ports like Karumba and Bing Bong, and cattle stations stretch across the Gulf Country behind them. It is a place of overwhelming horizontal space, where the drama comes not from height but from sheer extent, of water, of sky, and of that improbable rolling cloud.