I keep remembering this movie, and thought it was called "The Quest" but when I type it into the internet, I get nothing, so here goes...

There is a boy who hangs around this pond/waterhole, and around the same time every day he notices (with dramatization, of course) massive bubbles come up from the beneath the water. The kid is like preteen I think... so eventually after so many days, he gets himself ready to go underneath the water to find out what is down there...
And lo and behold it is just some mechanical machine where huge air pockets gather in it's crane-like device... they build up, disperse, and cause the major confusion...
.. but I think I remember the kid getting stuck in the machine, under water... :confused:

If anyone has any idea, please let me know so that I may sleep well, again... =) (j/k)

People love this movie. It's the Australian flick Frog Dreaming (aka The Quest) from 1986, starring Henry Thomas.