Underwater Movie Camera Maybe SOMEONE Remembers This Movie.?

Maybe SOMEONE remembers this movie.? - underwater movie camera

In the 80s I saw a movie about a movie channels that I really enjoyed it. Was conducted in Australia, where a teacher must protect students a hidden evil.

The details I remember are the head of the children escape through the interior of the poor, they entered a cave under the water and swam to reach the other side of the cave, and at the end of the film increase slowly in the heart of one of the bad guys "in a pot on the windowsill of the school.

Others have been answered on the basis of less detailed, and you are so clever ... I know someone knows! Thank you!