Looking for the name of this movie that I believe is from the 1980s. There is an abandoned quarry that is filled with water. A couple of kids are playing around it and discover there is something in the water. One of them may have even drowned by the supposed creature? (Can't remember.) The big reveal is that it is an excavator under the water and the scoop rises up every now and then due to gases rising from the quarry floor and collecting in the scoop.
14 year-old American kid Cody Walpole has been forced to go and live in the Australian Outback with his father’s best friend following the death of his parents. Cody is an enterprising inventor. He and two local sisters trek up to the lake near an old disused mine, which is said to contain the Donkejin or Bunyip, a creature from Aboriginal legend. When the girls drift out onto the lake on a raft, Cody jumps in to save them but they are attacked by a saurian monster that rises to the surface. Escaping and returning to town, Cody starts to research into ‘kadaicha’ or Aboriginal magic, and determines to return and confront the ‘Donkejin’. When he successfully makes a suit, he dives in to explore and find the creature.
In reality the creature is an old piece of mining equipment called a Donkey Engine. It’s basically an huge excavation crane that has had air trapped under it causing it to life to release some of the pressure from time to time. Cody managed to find his way into the air pocket underwater, and as the “creature” lift’s its head out of the water he finally manages to escape to freedom.