A very different kind of science fiction tale is Avalon Beyond the Abyss. An island blows up leaving a poison and a team is sent to investigate and clear up the threat to marine life. They discover a deep chasm and a large underwater cave with painted figures. A battle develops between the expedition leader and one of the team over the extent to which there is time and resources to investigate what can be seen in the cave.
Just when the leader orders the team to leave an expert arrives with the authority to investigate further and her findings appear to indicate a prehistory and the existence of either extra terrestrial to super beings. The man who presses for the work to continue dies in an attempt to explore further. The leader of the team elects to descend to the depths of the Abyss as seismic activity indicates the opening is closing. He provides maker for the body of the tam member so it can be raised to the surface. However on reaching the depths he has an experience which changes his understanding of the balance between science and the paranormal. He encounters someone who appears to be himself and also an alive comrade whose body has been raised to the surface.
I remained confused if this made for TV film was suggesting a form of heave or a parallel universe or something else. He returns to the surface against the odds a change man. The gap in the oceans closes and with it proof of his experience. The poison stops and the marine earth is saved.