Q:

Flooded quarry monster revealed to be excavator

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.

A:

Frog dreaming? It's also called The Quest.

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.

