Context: Somewhere in harbourside Sydney, Australia, a family lives within a high-rise apartment building where the mother is preparing a meal and listening to the radio. Her fourteen year old daughter (Jenny Agutter) and six year old son (Luc Roeg) swim in the building's pool overlooking a view of the ocean while their father (John Meillon), deep in troubled thought, watches them from their balcony.One day, the father takes his children, still in their school uniforms, on a picnic into the Outback. He parks the car and reads while his daughter sets up a blanket with their lunch. Her brother plays nearby with his water gun and toy soldiers. Suddenly, and for reasons unclear to his children, the father announces it is time to go and brandishes a gun, firing several shots at them. The boy thinks it all to be a game but his sister understands the danger and shields her brother as they run from their mad father. She watches in horror as her father returns to the car and sets it on fire before seating himself within and putting a bullet into his head. Quickly, and keeping her brother's eyes averted, the girl retrieves their radio, a scarf, and what food she can carry before setting off into the wilderness with her brother.The siblings walk for hours under the hot sun, calmed by irrelevant radio broadcasts, and walking past a host of wild creatures. Come nightfall, they make a crude camp for themselves, much to the boy's delight. In the morning, the girl leads them up a rocky hillside where she hopes to find some bearings. However, she can see nothing but a broad spanse of wilderness. When they finish their lemonade, the girl opens a can of vegetables from which they drink the juice. Recalling an uncle's story of military training, the girl suggests they eat salt to retain water and surmises to her brother that they may spend some time in the desert. She remains stoic, but wary, while her brother is blissfully unaware of their situation, remaining entertained by the radio and his toys. Eventually, after becoming filthy and tired, they come upon a lone tree standing over a pool of water where parakeets flock and feast on fallen fruit. The boy puts on in his mouth and proclaims that it 'tastes lovely'. They wash in the water and the girl scolds her brother to take care of his clothes so they will last. When he asks if they are lost, the girl replies that they are not, trying to remain chipper. They sleep to the sounds of the radio as night animals stir around them.In the morning, the girl wakes to find that their water hole has dried up and the fruit has either been eaten or spoiled. The girl decides to remain where they are, hoping that the water will return. As they nap in the hot sun, the boy spots an aborigine youth (David Gulpilil) pursuing an animal for food. They make contact and the children attempt to communicate with the aborigine boy. However, he does not understand their language and merely stares at them with curiosity. The girl repeats their need for water but the word is incomprehensible to the aborigine. When her brother mimics drinking, the aborigine understands and shows them how to dig for water using a hollow tube to drink through. Assuming that he will lead them to civilization, the siblings accompany the aborigine, unaware that he is on a 'walkabout', a coming-of-age journey that every male aborigine youth must take alone in order to be initiated as an adult in his tribe.As they travel the Outback, the aborigine kills and harvests food for them, giving them all plenty to eat and drink. The move from the desert to greener pastures and forests where wildlife becomes plentiful. When the boy becomes sunburnt from going shirtless, the aborigine rubs pig fat on his back to alleviate the burn. While communication between them remains limited, the trio share food and play together, though cultural differences are evident; the boy attempts to share his toy soldiers with the aborigine, but he finds no use for them and tosses 
 Question: what has dried up By the next morning?
Output: their water hole has dried up.